A Literature Survey on the Additional Costs of Living for People with Disabilities

Abstract

The existing literature estimating the additional costs of living faced by people with disabilities is still scarce, despite its relatively long existence. At the moment, existing studies have focused mainly on EU, Anglo-Saxon countries, Malaysia, the Philippines, Ghana, Vietnam, Cambodia, one state in India, sub-Saharan Africa, and China. This limited geographical coverage provides certain estimates for a large fraction of the OECD countries, along with non-representative samples from most other countries, leaving behind more than 75% of the countries worldwide. The main disadvantage of the scarcity of studies relates to the difficulty in estimation and the unavailability of data on disability and related costs. This study surveys the literature on the additional costs of living for people with disabilities. It summarizes the models of disability, the categorization of different costs, the cost assessment methods, and the reasons for difficulty in measuring/estimating costs. We present all studies in the literature received estimating the additional costs of living for people with disabilities, along with the methods used and the geographical areas investigated. The main conclusions drawn from the present survey point to significant additional costs of living for people with disabilities, depending on the type and intensity of disability, which in all cases are not less than 20% of household income, and increase significantly depending on the specifics.

1. Introduction

Disability is a complex phenomenon of great concern to modern society, in both the developed and the developing world, with health, social, economic, and psychological dimensions. It complicates (and often deteriorates) the lives of millions of people who, consequently, face numerous difficulties in safeguarding a standard of living comparable to individuals without disabilities, mainly through the creation of additional expenditures. These difficulties are largely eased when the necessary financial resources are available. Thus, it is crucial to have an accurate understanding of the additional costs borne by different heath conditions pertaining to disability in order to recommend and form adequate and appropriate public policies. At the same time, it is crucial to highlight that financial resources cannot accommodate all difficulties, and that numerous other adjustments and provisions, such as environmental accommodation, access to adequate medical care, societal acceptance, and support for human rights, are necessary to improve the standard of living for people with disabilities.

Individuals with disabilities face higher expected and other unexpected expenses due to disability. Therefore, unless an income boost becomes available to them through public expenditures or provision of public goods, they are typically forced to lower their standard of living, as compared to individuals with no disabilities, ceteris paribus.

Provision of additional income and public goods and services to individuals with disabilities is complex for the additional reason that not all disabilities are of the same type or the same severity level, while a considerable fraction of disabled individuals face multiple types of disability simultaneously. This multidimensionality complicates the assessment of an individual condition, adding extra burdens in the design and implementation of the aforementioned policies.

As reported by Eurostat, in all European Union (EU) Member States, people with disabilities were more likely to face difficulties making ends meet in 2021 compared to people without disabilities. In Greece, 76.6% of people with disabilities faced such difficulties compared with 50.5% in neighboring Bulgaria. Lower rates are found in Sweden (15.8%), Luxembourg, the Czech Republic (14.9%), Denmark (13.6%), the Netherlands (11.2%), Germany (10.6%), and Finland (10.1%)1.

The main conceptual issue associated with the estimation of the additional costs of disability is the definition of disability itself. Although the disability concept was initially introduced for religious reasons, the first formal approach provided in the literature was the medical definition (Clapton 1997). According to Clapton (1997), disability is an impairment. This impairment limits access to certain goods and services and, as a result, individuals with disabilities are not able to participate fully in society. According to this approach, the impairments are handled through interventions, either rehabilitation or provision of special services. On the other end, the social model, mostly based on the work by Oliver (1983) and rooted in the Union of the Physically Impaired Against Segregation, and Disability Alliance (1976), views disability as a problem of social factors. In this approach, the inability of an individual to consume certain goods and services is due to lack of infrastructure and appropriate conditions that society is unable to offer. The later-introduced “bio-psycho-social model” (World Health Organization 2011) offers a workable compromise between the two. All models are presented in detail in the following section.

The current literature proposes different ways of calculating the additional costs of living for people with disabilities, while there is no consensus regarding the most appropriate or accurate one. Existing studies approach the topic through different methods and datasets, often offering diverging conclusions.

This paper aims to provide a survey of the existing literature on the additional cost of disability and discuss the different approaches and methodologies available. Despite the relevant scarcity in the field, this is an evolving strand of literature with significant implications for policy formation, while additional efforts are required to further streamline the existing theories and methods and provide higher accuracy of the estimates. The previous systematic review by Mitra et al. (2017) includes 20 studies published up to 2014. Our review contributes to the literature by summarizing the studies, the methods, the geographical scope, and the main findings of existing studies up to date. The review highlights the existing definitions of disability, the models of disability, the categorization around different types of additional costs due to disability, and the methods for estimating the additional costs of living due to disability, in addition to important contributions, remaining gaps, conflicting findings, and areas presenting room for improvement in estimating the additional cost of living due to disability.

Section 2 will present different models of disability. Section 3 will review the literature estimating the additional living cost of people with disabilities. and Section 4 will conclude.

2. Relevant Sections

2.1. The Models of Disability

A key concept related to the determination of the additional costs of living for people with disabilities is the definition of the concept of disability. A key prerequisite in any methodological approach to the additional costs of living with a disability is that both researchers and the public can understand the concept in the same way.

To be able to understand the concept of disability, one needs to understand the models of disability which have been created over time, based on different definitions. Initially, the concept of disability was formed for religious reasons, mainly rooted in the beliefs of Western Judeo-Christian society. Based on this conceptualization, disability was an act of a higher being and presented as an opportunity for miracles. This perspective was displaced by the expansion of medical and scientific knowledge and by the replacement of religious leaders with doctors and scientists as a “cognitive principle” in social values and therapeutic processes.

Over the past 50 years, the medical and social models have been considered as the two most prominent models for disability (Haegele and Hodge 2016). Disability, based on the medical model, is defined as an individual and/or a medical phenomenon that leads to limited functionality that is considered insufficient. Also, disability is regarded as the result of damage to the functions and structures of the body, including the mind, and can be caused by illness, injury, or health condition. This view combines impairment and disability with illness and the “sick role”. Disability, based on this approach, is considered as a problem that must be treated medically so that individuals can function within society (Haegele and Hodge 2016).

The medical model of disability, which the UN Convention on the Rights of Persons with Disabilities (CRPD) tries to overcome, sees disability as something that can be treated, corrected, or at least rehabilitated. Disability is considered as a deviation from the normal state of health. The exclusion of disabled people from society is seen as an individual problem, with the reasons for the exclusion being found in the impairment. According to the medical model, disability remains the exclusive responsibility of the aid and medical professions: doctors, nurses, special education teachers, and rehabilitation specialists.

Forty years ago, Oliver (1983, as cited in Oliver 2013) introduced the social model of disability, and his idea came from the document “Fundamental Principles of Disability”, that was first published in the mid-1970s. According to this model, people are not disabled by their disabilities but by the disability barriers they face in society. According to the social model, disability is the result of the interaction of the functional state of a person and his environment. People with disabilities are not identified based on their medical condition, but based on the environment that creates obstacles, when they try to take part in the social and economic life of their communities (Braithwaite and Mont 2009). In addition, the exclusion of disabled people from society is analyzed politically because of barriers and discrimination (Degener 2016).

The social model distinguishes between impairment and disability. Impairment is related to a condition of the body or mind, and disability is the result of how the environment and society respond to that impairment. Impairment is considered as an abnormality of the body, such as limitation or dysfunction of a limb, whereas disability is regarded as the disadvantage or limitation of activity caused by a social organization that does not consider people who have disabilities and excludes them from community life (Haegele and Hodge 2016).

The social model was largely aimed at professionals, and Oliver suggested that those who worked with people with disabilities reorient their work to a context based on the social model rather than the individual model, which had until then been largely followed, to make their practice more relevant to the needs of people with disabilities.

Oliver (as cited in Degener 2016) termed the medical model of disability as an ideological construction of disability through individualism and medicalization. The two assumptions on which the medical model of disability is based are considered according to Degener (2016) to have a dangerous impact on human rights: (1) disabled people must have housing and welfare, and (2) impairment can preclude legal capacity. The first case legalizes separate facilities for people with disabilities, such as special schools, living institutions, or sheltered workshops. The second case has led to the creation of mental health and guardianship laws that take an incapacity approach to disability. The social model was probably the philosophical basis of the treaty. One of the main achievements of the UN CRPD is the shift from the medical to the social model (Degener 2016). The transition from a “medical model” to a “social model” is defined as the process in which people are characterized as disabled by society itself rather than by their own bodies (World Health Organization 2011).

In the United States, the most widely used conceptual models of disability are the World Health Organization’s “International Classification of Functioning, Disability, and Health” (ICF) and a conceptual model of disability developed by Saad Nagi (1965, 1976, as cited in Stapleton et al. 2008). Since both models consider disability as a dynamic process involving the interaction of a person’s health status with other personal characteristics and with the physical and social environment, they are considered as “social” or “medical-environmental” models of disability. According to Stapleton et al. (2008), the two have replaced the traditional “medical model”, which considers health conditions to be the sole cause of disability.

Another disability model is the “bio-psycho-social model” (World Health Organization 2011), which is a workable compromise between the medical and social models. Based on this, disability is expressed as a set of isolations, activity restrictions, and intake restrictions, which have to do with negative aspects of the interaction between a person (with a health condition) and related factors that may concern that person, such as environmental (products and technology, the environment, support and relationships, attitudes, services, systems, policies) and personal factors (motivation and self-esteem) (World Health Organization 2011).

The World Health Organization (World Health Organization 2011, created the “International Classification of Functionality, Disability and Health” (ICF), which applies a bio-psycho-social model to measure how a person’s health, disability, and environment affect their ability to function. The ICF is the recommended measurement framework and standard for various applications in disability assessment.

Alyafei and Chauhan (2025) argue that the bio-psycho-social model offers the best context to understand disability, because it assesses how a person’s health, disability, and environment affect their ability to function. The bio-psycho-social model includes aspects of both the medical (biological) and the social (social sector) models of disability, while considering the person’s beliefs and attitudes about their disability and how it influences behaviors at work (psychological field) (Whelpley et al. 2023). As for the biological component, it contains mental and physical damage, while the psychological component focuses on the emotional state of the individual and personal or religious beliefs (Alyafei and Chauhan 2025).

Hunt (2024) considers the bio-psycho-social approach to be a holistic approach because he proposes that health and disease should be understood “holistically”. For this reason, biology, psychology (thoughts and behavior), and social context (levels of social support) should be considered. Thus, the holistic bio-psycho-social framework should recognize the broader social (political) context that has shaped this model and recognize how the model and related practices can contribute to chronic illness and disability. Finally, he considers that the holistic framework of the bio-psycho-social model leads to recommendations for social health policy and practice that address what is wrong with society as opposed to what is “wrong” with the individual.

Another important factor is that society needs to find ways to include people with disability in social, economic, and political activities, supporting them and providing them with equal opportunities (Petasis 2019). Therefore, the bio-psycho-social model of disability adopts a broader and more integrated approach to disability by considering all the factors that affect how disability affects a person (Tait and Silveira 2023). The bio-psycho-social model is a holistic model of clinical care and doctor-patient interaction, which promotes the doctor-patient relationship through the physician’s understanding of the patient’s perspective on their medical illness and by integrating the biological, social, and psychological aspects of their care (Persaud-Sharma et al. 2020).

The medical model and the social model are presented in the literature as dichotomous, but disability should not be considered either as purely medical or as purely social, since people with disabilities can often face problems caused by their state of health (World Health Organization 2011). Even though historically the dominant models that have framed disability have been the medical and the social models, the bio-psycho-social model presents an overarching framework that captures all different aspects. For a better understanding and consolidation of the models available in the literature, refer to

Table 1. Comparison between the medical, social, and bio-psycho-social models of disability discourse. Source: Haegele and Hodge (2016). (For the creation of the following table, the table by Haegele and Hodge (2016) was used, to which we added an additional column concerning the bio-psycho-social model).

Topic	Medical Model	Social Model	Bio-Psycho-Social Model
What is disability?	An individual or medical phenomenon resulting from impairments to the functions or structures of the body, or from a deficiency or abnormality.	A social construct imposed on top of impairments by society; a difference.	Interaction between health conditions and personal and environmental factors.
Access to treatment or services.	Referral by diagnosis.	Self-referral; experience-driven.	Provides a holistic approach to the treatment of disability.
Targets of interventions	“Fixing” a disability to the maximum extent possible; “normalizing”.	Social or political change in an effort to reduce environmental barriers and increase levels of understanding.	Biological, social, and psychological factors are taken into account.
Outcome of interventions	Normalized function; functional member of existing society.	Self-advocacy, changes in environment and understanding, and social inclusion.	Increased participation, improved quality of life, and reduction in social barriers.
The agent of remedy	The professionals.	Can be the individual, an advocate, or anyone who positively influences the arrangements between the individual and society.	Holistic intervention.
Effects on individuals who are typically functioning	Society remains the same.	Society evolves to be more inclusive.	Society is actively changing its structures, policies, and attitudes to become more accessible and inclusive.
Perceptions towards individuals with disabilities	The individual is faulty.	The individual is unique.	Integrated approach by taking into account all the factors that affect the way disability affects an individual.
Cognitive authority perception of disability	Scientists and doctors perceive disability as negative.	Academics and advocates with disabilities perceive being disabled, in itself, as neither positive nor negative.	Doctor–patient relationship, understanding the patient’s perspective on their medical illness, and integrating the biological, social, and psychological aspects of their care.

.

Besides the theoretical foundation, all three models presented above are not equipped with a methodological approach for estimating the additional costs of living for people with disabilities. In addition, the estimation methods presented in Section 3.2 do not stem from the medical, social, or biopsychosocial models in the elements to be accounted for. They simply present a “how-to” measure without differing in what they capture. However, the important aspect in which the different estimation methods are influenced by the three theoretical models of disability presented above is in the way they classify disability, i.e., who is considered as disabled and how severe their disability is assessed to be, depending on the model followed by the authors. According to Antón et al. (2016), although much of the literature is based on the living standards approach, the overall results of this literature are extremely difficult to summarize because authors rely on different definitions of disability and consequently use different variables and econometric specifications to estimate the costs of disability. This makes the results difficult to compare. For example, Minh et al. (2015) use the WHO ICF definition of disability, which, as discussed above, is based on the bio-psycho-social model of disability, whereas Loyalka et al. (2014) use the traditional medical model of disability. Despite this difference in the definition of disability, both Minh et al. (2015) and Loyalka et al. (2014) use the Standard of Living (SoL) method.

2.2. Definition of Additional Costs of Disability

As reflected in the literature, there is no specific definition of “additional cost”, but this additional cost results from the additional needs of people with disabilities. Each methodology that aims to measure these costs approaches the needs of people with disabilities in a different way. Other studies take these needs into account (subjective and budgets standards) and others do not (standard of living and cooperating); those methods which do not consider people’s needs differentiate between the resources needed by people with and people without disabilities. We hereby present the different definitions of additional costs available in the literature.

All attempts to classify disability costs, since the first studies in the literature, exhibit two main themes, i.e., disability-specific and general items, despite their differences. Large (1991) distinguishes the additional cost of disability into two economic implications related to disability: an opportunity cost and an explicit cost. The opportunity cost refers to income loss for the caregiver (partner, parent, etc.), due to partial or full inability to work. The explicit cost stems from the additional expenses which arise due to a health condition and can be either capital or revenue. Capital costs can be distinguished into disability-created capital costs and disability-enhanced capital costs. Disability-created costs are expenses for basic or specialized equipment, which arise solely due to disability and are not provided through public services or the public health care system. Examples of such expenses are wheelchairs, special beds (beds with wheels), special mattresses for beds, special computers for the blind or deaf, etc. Disability-enhanced capital costs concern goods that would otherwise be classified as luxuries by a person without disability, such as electronic can openers or door phones adjustable with remote control (Wood and Grant 2010, p. 32). An intermediate category among the above capital costs is the cost required to convert a home to make it accessible to a person with a disability.

Berthoud (1991) adds a third cost compared to Large (1991), typically undertaken by public organizations or NGOs/non-for-profit organizations offering treatment, care, or other personalized services to people with disabilities free of charge. To assess this third cost, one should treat the opportunity and the explicit costs affecting it as stable. In addition, he follows a different conceptualization with regard to the categorization of additional costs of disability and lists four types:

• Needs vs. cost: the end products that a person with a disability needs are the same as those that any person needs. The difference is that the disabled person needs to spend money on a caregiver, extra fuel, and a car to be able to obtain these things.
• One-off costs vs. recurring costs: conversions to a dwelling to make it accessible to a person with a disability are one-off and are considered a capital element, while spending on fuel, food, and clothing is considered a recurring expense.
• Special costs vs. additional costs: some goods and services may be purchased solely due to disability, and some people will not need them at all. For items used by both disabled and non-disabled people, people with disabilities will be forced to spend much more.
• Extra costs vs. reduced costs: disability can increase spending on some goods while reducing it on others.

Tibble (2005) gives a definition of “extra costs”, which is used in most studies, to be “the costs of persons with disabilities for needs not covered by free/subsidized services” (p. 3). The costs described by Tibble (2005) are essentially the same as the capital costs introduced by Berthoud (1991) and Large (1991) above, exhibiting less variation in the respective classification. These are the same types of costs also described by Mitra et al. (2017) and a later study by the Center of Inclusive Policy (2024). They are divided into two categories: (i) general items that any household may need (health care, food) and (ii) disability-specific items needed by persons with disabilities (assistive devices, rehabilitation, personal assistance, home adaptations). General costs, however, may be higher for people with disabilities because of their specific needs (transportation and medical care).

Tibble (2005) highlights that increases in costs and their variation depends on the following factors: the type of disability (impairment), the severity of the disability (impairment), the composition of the family (household), the income, the geographical location, and the amount of free or subsidized services provided by voluntary or statutory organizations.

3. Discussion

3.1. Cost Assessment Methods Available in the Literature

With regard to the additional costs of disability, studies have not come to a consensus regarding their size, as well as (i) the factors affecting additional costs, and (ii) the best method to measure or estimate them. An extra burden is added by the difficulty to conceptualize “extra costs” in order to measure them. Despite all the disputes in the literature received, there is a strong consensus that disability entails significant additional costs.

One of the first studies addressing the extra cost of disability was conducted by Berthoud (1991). According to Berthoud (1991), the financial “costs” of disability can be described in a wide range of ways. One is the loss of income experienced by many people with disabilities or faced by their relatives if they must leave their jobs to take care of them. This is the same as the implicit costs introduced by Large (1991) in the previous section. A second way is the cost to public or voluntary organizations of treatment, care, training, or other specialized services provided free of charge to people with disabilities. Finally, a third way is the extra costs of living faced by people with disabilities.

Berthoud (1991) mentions three possible ways of measuring the additional costs of disability:

• Direct questions: asking individuals how much extra they spend on related items. The comparison involves how they would spend their money if they were not disabled. They could also be asked if there are items they spend less on because of their disability. This method is conceptually accessible but may not be accurate because it requires detailed reporting of costs by respondents.
• Expense diaries: taking detailed measurements of all expenses from a sample of people with disabilities and comparing the results with the corresponding data of people without disabilities. The findings, within a fixed total expenditure, show both increases and decreases in costs, making it difficult to interpret as a net additional cost. It is a reliable method, as both sides of the comparison are based on facts rather than speculation. There is, however, a difficulty in analysis and interpretation, due to the positive and negative coefficients added to the equation.
• Standard of living: looking for evidence of a decline in living standards which people with disabilities can cope with on a given income. Because the expenses that people make are derived from their income, calculating the cost of disability must consider the reduction in the general standard of living that people with disabilities have, as a result of minimizing other expenditures on things they need because of their disability.

In the current literature (Tibble 2005; Berthoud 1991; Stapleton et al. 2008; Zaidi and Burchardt 2005; Antón et al. 2016; Cullinan et al. 2008; Indecon 2004; Cullinan et al. 2011; Pino and Pérez 2011; Loyalka et al. 2014; Minh et al. 2015; Morris et al. 2022; Palmer et al. 2018; Morris and Zaidi 2020; Smith et al. 2004), there are different perspectives regarding the categorization of cost measurement methods. One is based and built on Tibble (2005) and presents similarities to other classifications by Berthoud (1991), Stapleton et al. (2008), and Zaidi and Burchardt (2005). These different approaches are not substitutes but have been developed either in parallel or by building on previous work. They differ in the measurement of individual needs along with the associated costs or in assessing actual expenses and resource allocation. Tibble (2005) normalized the methodological approaches of costs he studied in his review into four general categories:

• Subjective approach: alternatively named as the “direct questions” approach (Berthoud 1991) or “required goods and services” approach (Stapleton et al. 2008). This approach is based on asking individuals how much extra they spend on specific items. The comparison has to do with how they would spend their money if they were not disabled. The main flaw of this method is that the questions refer to a hypothetical scenario. A key advantage of this approach, according to Tibble (2005), is that estimates of increased costs are provided by people with disabilities themselves. In addition, depending on the way the questions are asked, the budget constraint, which is an obstacle to the accuracy of the comparative method, may also be partially compensated.
• Comparative approach: this approach parallels the “expenditure diary” used by Berthoud (1991) and the “goods and services used” approach referred to by Stapleton et al. (2008). It is based on keeping a diary of all expenses and comparing the results with the corresponding data of people without disabilities. Expenses of people with disabilities, through this method, are found to be either higher or lower than those of people without disabilities. Despite the reliability of the method, the interpretation becomes cumbersome mainly due to the opposing direction of the different effects. This approach is further hampered by respondents’ budget constraints, as there is no option to measure how much respondents would spend if their income were not constrained. As a result, this method cannot measure the potential cost of disability.
• Standard of living approach: According to Zaidi and Burchardt (2005), the additional disability costs result from a comparison of the “standard of living” of households with disability to that of households without members with disabilities (Tibble 2005), based on a given income and tested for other sources of variation. This method, initially introduced by Berthoud (1991), is similar to the “expenditure equivalence” approach by Stapleton et al. (2008).
• Budget standards approach: developed by the Center for Research in Social Policy (CRSP), resembles the subjective approach above, as people with disabilities are directly asked to state their needs. It does not measure the extra costs but presents the income required to achieve a certain standard of living.

All the above, in a sense, boil down to Sen’s (1985, 1987, as stated in Antón et al. 2016) concept of “distributive justice”, based on the equalization of people’s basic abilities. After all, what public policies should target is safeguarding a minimum standard of living for all individuals, ceteris paribus. The basic idea is that the standard of living is a matter of functions and capabilities, targeting a minimum objective level of living associated with a minimum level of real income. According to Sen, goods are not relevant in themselves. What is important is the usefulness that people receive when using the goods, which directly relate to their characteristics and properties. Thus, it is the ability of the individual to convert characteristics into different combinations of function that gives them the ability to achieve a certain level of well-being (Antón et al. 2016).

A more recent attempt, by Mont et al. (2023) splits the methodologies into two main branches (a) Current Expenditures, which measures what is currently being spent, and (b) Full Participation, which measures what would be spent (hypothetically) if equal participation were possible.

The Current Expenditures approach introduced by Mont et al. (2023) includes three methodologies:

• The Goods and Services method (initially introduced by Mont and Cote 2020): which is effectively the same as the Comparative Approach of Tibble (2005) above and the “Goods and Services Method” of Stapleton et al. (2008).
• The Standard of Living (SoL) method: which is the same as the SoL method above (Berthoud 1991; Zaidi and Burchardt 2005; Tibble 2005).
• The Patterns of Expenditures method: which resembles the budget standards method above.

Full Participation is based on the Required Goods and Services, a qualitative approach, with teams of experts representing the diversity of people with disabilities, parents of children with disabilities, rehabilitation professionals, and other service providers, who, together with the input from focus groups of people with different types of disabilities and support persons, decide on the goods and services needed and then price them.

Table 2. Literature estimating the additional costs of living for people with disabilities.

Study	Country and Data Source	Population and Disability Definition	Indicators	Estimate of the Additional Cost
Amin and Adros (2019)	Malaysia: Survey on Staff in International Islamic University Malaysia (IIUM).	Definition of disability according to the CRPD (United Nations 2006)	SoL Proxy: consumer durables.	Households containing one person with disabilities accounted for 27.5% of their monthly income.
Antón et al. (2016)	31 European countries: 2007–2012 European Union Statistics on Income and Living Conditions.	Household population; Difficulty making ends meet; access to a set of services and assets.	SoL Proxy: welfare indicator.	Significant diversity in the cost of disability exists across European countries, with Scandinavian countries at the top of the ranking and Eastern European states at the bottom.
Asuman et al. (2021)	Ghana: Seventh Ghana Living Standards Survey (GLSS7).	Household population; Disability is defined by GLSS 7 as the consequences of lifetime impairment.	SoL Proxy: an indicator of the presence of a PWD in the household.	26% of total annual household consumption expenditure.
Braithwaite and Mont (2009)	Bosnia and Herzegovina (Bosnia) and Vietnam: Household Surveys on Living Standards.	Household population; World Health Organization’s International Classification of Functioning, Disability and Health and the UN’s Washington Group (WG).	SoL Proxy: asset index of the seven durable goods most commonly held in the two countries.	For Vietnam, 9%, and for Bosnia and Herzegovina, 14% additional expenditures are due for the most commonly owned durables.
Carraro et al. (2023)	The Philippines: Disability ID card lists provided by Local Government Units (LGUs).	Household population; United Nations Convention on the Rights of Persons with Disabilities (CRPD).	SoL Proxy: an asset index.	40% and 80% extra expenditure to reach the same living standard as other children.
Center for Inclusive Policy (2024)	India: Data collected from experts and focus groups.	Persons with disabilities and their representative organizations; Rights of Persons with Disabilities Act 2016 (RPDA), medical model of disability.	Goods and Services Required (GSR).	The government could provide goods and services to people with disabilities at a rate of 0–30% of the total required goods and services
Cullinan et al. (2013)	Ireland: 2001 Living in Ireland Survey	Household population with older persons; Severity of illness or condition.	SoL Proxy: Consumer durables.	Disabled with severe limitation: 79.4% of disposable income (YD); disabled with some limitation: 20.8% (YD); disabled with no limitation: 28.8% (YD).
Cullinan et al. (2011)	Ireland: 1995–2001 Living in Ireland Survey	Household population; Any chronic health problem.	SoL Proxy: Consumer durables; Holidays.	Long-run economic costs of living associated with disability: 32.7% of income for severely disabled; 30.3% of income for somewhat limited disability. Short-run costs: 37.3% of income for the severely disabled and 20.3% of income for those with somewhat limited disability.
Cullinan et al. (2008)	Ireland: 1995–2001 Living in Ireland Survey	Household population; Social model.	SoL Proxy: Consumer durables; Holidays.	Average cost of disability is 22.2% of disposable income.
Indecon (2004)	Ireland: Household Budget Survey (HBS)	Household population; Receipt of disability welfare payment.	DSA, EDA, and SoL Proxy: Consumer durables.	EUR 143 per week SOL
				Spinal Injury: EUR 244 per week. Down’s Syndrome: EUR 130 per week. Vision Impairment: EUR 81 per week. Schizophrenia: EUR 42 per week. DSA
				Spend more on fuel and lighting, therapeutic equipment, and medical expenses. EDA
Jones and O’Donnell (1995)	UK: 1986–1987 FES Disability Survey	Household population; Disability is defined in accordance with the International Classification of Impairments.	SoL Proxy: Individual goods and groups of goods.	Costs of fuel and transportation are 45% and 64% higher, respectively, for a two-adult household with a disability
Loyalka et al. (2014)	China: 2006 National Survey of Disabled Persons	Household population; Medical impairments.	SoL Proxy: Index of ownership of consumer durables.	The extra costs of “any” disability, as a percentage of income is: 31.1% for one-adult households in urban and 26.4% in rural areas; 27.8% for two-adult households in urban and 26.3% in rural areas; 28.2% for three-adult households in urban and 17.5% in rural areas.
Minh et al. (2015)	Vietnam: 2011 Survey data from 8 cities and 6 provinces	Household population; Functional impairments.	SoL Proxy: Savings as index of household assets.	8% to 9.5% of annual household income.
Mont et al. (2022)	Africa (sub-Saharan Africa, Ethiopia, Tanzania, Liberia, Nigeria, Namibia, Zimbabwe, and Malawi): Ethiopia, Socioeconomic Survey 2018/2019; Tanzania, The National Panel Survey 2019/2020; Liberia, Household Income and Expenditure Survey (2016); Nigeria, Living Standards Survey 2018/2019; Namibia, Household Income and Expenditure Survey 2015/2016; Zimbabwe, Poverty, Income, Consumption, and Expenditure Survey Questionnaire 2017; Malawi, Integrated Household Survey and Integrated Household Panel Survey 2019.	Household population; household has at least one member with a disability after responding “great difficulty” or “cannot do” in at least one of the six activities of the WG Short Question Set.	SoL Proxy: Asset index based on a comparable set of assets across countries.	Households in Ethiopia with a member with a disability need 6% more income to maintain their SOL; in Zimbabwe, it is 4%, and in Tanzania, it is up to 10%.
Mont and Cuong (2011)	Vietnam: 2006 Vietnam Household Living Standards Survey.	Households; International Classification of Functioning, Disability, and Health; Social model.	SoL Proxy: Asset Index.	Households that include a person with a disability are close to the poverty line. Poverty rates increase significantly when the poverty line is adjusted for the 11.5% value of the seven most commonly held assets.
Morciano et al. (2015)	UK: 2007/2008 Family Resources Survey.	Older people above the state pension age; latent factor model for disability.	SoL Proxy: Ten indicators of ability to afford items or activities, constructed into a latent index.	62% of net weekly pre-disability household income for an older adult with a median level of disability.
Morris et al. (2022)	U.S.A.: U.S. adult population: 2015 and 2018 waves of the National Financial Capability Study (NFCS); 2018 wave of the U.S. Financial Health Pulse Survey (PULSE); 2016 Financial Well-Being Survey (NFWBS); and 2018 Survey of Household and Economic Decisionmaking (SHED).	Household population; International Classification of Functioning, Disability, and Health has become the data standard in which the U.S. government uses to measure disability (U.S. Census Bureau 2017).	SoL Proxy: Index measures of material deprivation.	29% more income to obtain the same standard of living as a comparable household without a member with a disability.
Morris and Zaidi (2020)	15 European countries: Survey of Health, Aging, and Retirement in Europe.	Household population: adults with disabilities aged 50–65; Work-disability; adequacy of social welfare programs.	SoL Proxy: Difficulty experienced by the household in making ends meet; material deprivation.	44% of income for a household with an adult reporting a work- related disability, and slightly less than 30% of income for a household with an adult who receives disability benefits.
Palmer et al. (2018)	Cambodia: 2009–14 Cambodian Socio-Economic Survey.	Household population; Functioning impairments.	SoL Proxy: Asset index combining durable goods and housing characteristics.	The direct cost of disability doubles the poverty rate among households with disabled members, rising from 18% to 37% of monthly household consumption expenditure.
Pino and Pérez (2011)	Spain: 2007 Living Conditions Survey.	Household population; Individuals with chronic illness or disability who are limited in their daily activities, and individuals suffering from a chronic illness or condition who are severely limited in their daily activities.	SoL Proxy: Durable goods; capacity to face unforeseen expenses.	40% and 72% of household income for households with moderate and severe disability, respectively.
South African Department of Social Development—SADSD (2015)	South Africa: 2011 and General Household Survey [GHS] 2011.	12 expert groups, 206 adults with disabilities and 62 caregivers; CRPD United Nations Convention on the Rights of Persons with Disabilities (CRPD) in 2007.	DSA Washington Group’s set of questions.	ZAR 130 to ZAR 2830 per month, where a person who needs an assistant relies on an unpaid family member.
Smith et al. (2004)	UK: Case study Participants were recruited in Derby, Birmingham and Nottingham via local and national disability organizations and groups.	78 people: men and women over 45 years of age, but under 60; Physical and sensory impairments.	Budget Standards Approach; Lists of items agree to be necessary to maintain a predetermined standard.	Benefits cover only 28% of the cost for those with low-medium needs, 30% for those who have intermittent or fluctuating needs, 35% for those with hearing and vision impairments, and 50% for those with high support needs.
Saunders (2007)	Australia: 1998/1999 Household Expenditure Survey.	Household population; Severity of activity restrictions.	SoL Proxy: Inverse of the count of positive responses to a series of hardship questions.	37% of equivalized household income, rising to 40–49% of income for those with a severe or profound restriction.
She and Livermore (2007)	US: 1996–1999 Survey of Income and Program Participation panel.	Age 25–61 at first interview; Condition that limits type or amount of work.	SoL Proxy: Ability to meet expenditures; material deprivation.	165–288% of poverty threshold income.
Zaidi and Burchardt (2005)	UK: 1996/1997 Family Resources Survey.	Household population; Severity categories of disability, SoL.	SoL Proxy: Ownership of consumer durables; Ability to save; Subjective assessment of the household’s financial situation.	11% of average income for those with a mild disability/impairment; 34% of average income for a moderate disability; and 64% of average income for a severe disability.
Wilkinson-Meyers et al. (2010)	New Zealand (2005–2007): the acceptability of the approach was achieved through a partnership with leaders and experts from the disabled community, and by adopting a process that facilitated the engagement of disabled people.	People of working age (18–64) with a physical, mental, mental, auditory, or visual disability, living in the community; Social model of disability; Mixed method.	Budget Standards Approach.	Additional cost of NZD 72.36 per week.

summarizes all studies estimating the additional costs of living for people with disabilities referring to the country, data used, definition of disability, estimation method, and main findings.

3.1.1. Expenditure-Based Approaches: The Direct Survey Approach

The DSA estimates the economic cost of disability and is alternatively called the subjective method. The direct survey approach entails directly asking people with disabilities or their caregiver how much extra they spend on specific items. In practice, the DSA is considered the simplest approach, as any additional costs identified can be aggregated to give an estimate of the total additional costs resulting from the disability (Cullinan et al. 2008). The Goods and Services (GS) method, classified as the Comparative Methods approach by Tibble (2005), is considered the most direct way of estimating the additional cost, since the survey is given directly to the individual facing the disabilities.

Based on the GS method, a study focusing on South Africa (South African Department of Social Development—SADSD 2015), estimated costs associated with basic consumption, care and support, as well as access to basic services and participation. 12 expert groups, 206 adults with disabilities, and 62 caregivers were surveyed. Their results point to a considerably wide range of estimated costs depending on the type of disability, and even among people with the same type and baseline level of disability, the level of support needs and economic status.

According to the Indecon (2004), this approach provides an indication of the types of costs borne by people with disabilities and a guide to the size of these costs, rather than accurate estimates of the additional costs of disability. In addition, it has been considered particularly useful for identifying areas of specific costs faced by people with specific disabilities. Based on this approach, Indecon (2004) conducted a survey on people with various types of disabilities, which were identified through their responses. Out of 1400 questionnaires that were sent by post, 248 were returned. The questionnaire asked respondents to identify the categories in which they incurred additional costs due to disability and to estimate the amount per category. Their estimates reveal an average weekly cost of EUR 244 for spinal injuries, EUR 130 for people with Down syndrome, EUR 81 for people with visual impairment, and EUR 42 for people with schizophrenia.

3.1.2. Expenditure-Based Approaches: The Expenditure Diary Approach (EDA)

The expenditure diary approach includes taking detailed measurements of all expenditures of a sample of persons with disabilities and comparing the results with data on corresponding expenditures from a sample of persons without disabilities. Also, since income is limited, extra spending on some items will lead to lower spending on other items (e.g., higher spending on heating may lead to less money being spent on new clothes). In this way, this methodology makes it possible to identify those areas where people with disabilities spend much more and much less than other households. A key disadvantage of the method is that it is administratively demanding, since it requires detailed and lengthy journaling, and the results are difficult to interpret. For their survey, they used data from the Household Budget Survey 1999/2000 (HBS) and an analysis of Indecon’s anonymous HBS data. Their sample consisted of 7644 households. The HBS asked participating households to complete an expenditure calendar fortnightly. The results of the survey showed that people with disabilities spend more on fuel and lighting, therapeutic equipment, and medical expenses (Indecon 2004).

Expenditure diary approaches are alternatively called comparative approaches, addressing some of the problematic issues in DSAs. A comparison of costs can be employed to establish areas where disabled people are prone to experiencing additional costs (Cullinan et al. 2008).

3.1.3. The Standard of Living (SoL) Approach

Most of the existing literature aiming to estimate the additional costs of living for people with disabilities are using the Standard of Living (SoL) approach. The SoL aims to establish the cost of disability by comparing households with disabled members to households without disabled members.

Figure 1 illustrates the theoretical relationship between income, standard of living, and disability used in the SoL method. Figure 1 illustrates the fact that people with disabilities will face a lower standard of living than people without disabilities with the same income. Otherwise read, it reflects the fact that to achieve the same standard of living as their counterparts, people with disabilities need a higher income.

Several studies using the standard of living approach refer to Sen’s theory and approach. More specifically, Sen (2004), as mentioned in Antón et al. (2016), distinguishes two main types of disability-related disadvantages. The first is what he calls the “profit disadvantage”, stemming from difficulties that people with disabilities face in finding a job or maintaining it, while receiving a lower salary. In addition, he highlights that disability can affect the acquisition or accumulation of human capital. The second is the “conversion disadvantage”, referring to the additional resources that people with disabilities require to achieve the same level of well-being as people without disabilities. Alternatively, due to a lack of resources, people with disabilities face more difficulties in achieving the same level of well-being as people without disabilities. This disadvantage is related to the social protection system, which through various policies, aims to compensate for the higher costs associated with disability. Despite the widespread use of the SoL method, the different definitions of disability, economic variables included, and econometric techniques used have created issues in the comparability of results.

The standard of living approach is influenced by the change in consumption patterns. This is because people with disabilities may have a lower standard of living than people without disabilities with the same level of income, which results from the diversion of scarce resources to goods and services required by disability. This creates a substitution in favor of disability-related consumer goods and away from goods that improve the general standard of living, which results from income restriction (Zaidi and Burchardt 2005, p. 94). The term “standard of living” is used instead of “well-being” and has more to do with the concept of material well-being than total utility. This approach calculates the additional cost of living incurred by individuals as a consequence of their disability but does not reflect any loss in the underlying well-being as a direct result of disability. Estimates do not include opportunity costs—loss of personal earnings or profits lost by friends and relatives who provide care without pay. Living standards are considered to increase with income for all households, but for households with higher needs, such as households with a disability, the same income leads to a lower standard of living. On the other hand, the same standard of living can be attained in a household with higher needs if it has a higher income. The standard of living approach to measuring additional disability costs is related to Rothbarth’s suggestion (Zaidi and Burchardt 2005) that the standard of living in households with different needs can be compared to the assessment of “excess income”, where excess income is what is available for spending on necessities. Below, we summarize the studies using the SoL method.

Studies conclude that the additional costs of disability are significant and vary with disability type (Zaidi and Burchardt 2005; Minh et al. 2015; Indecon 2004), while increasing with severity level (Zaidi and Burchardt 2005; Cullinan et al. 2011; Pino and Pérez 2011; Loyalka et al. 2014; Mitra et al. 2017; Amin and Adros 2019; Cullinan et al. 2013; Carraro et al. 2023; Saunders 2007; Indecon 2004) and type of household (Loyalka et al. 2014; Morris et al. 2022; Zaidi and Burchardt 2005), among which households with married couples face lower costs. Findings also suggest that the cost of disability increases as the number of household members decreases (Cullinan et al. 2013). Limiting the focus to samples of older individuals, Morciano et al. (2015), Morris and Zaidi (2020), and Cullinan et al. (2013) verify the sensitivity of disability costs to disability type, severity, and type of household.

With regard to disability types, the literature concludes that adults with cognitive disabilities in the US (Morris et al. 2022) and mental health in the UK (Zaidi and Burchardt 2005) face the highest costs compared to other types of disability. For China, Loyalka et al. (2014) conclude that households with intellectual, mental, and speech disabilities tend to have lower incomes than households with other types of disabilities.

On the estimates of the additional costs of living for people with disabilities, the findings are summarized as follows: Jones and O’Donnell (1995) estimate the costs of fuel and transportation in the UK to be 45% and 64% higher, respectively, for a two-adult household with a disability compared to a similar household without a disability. Cullinan et al. (2011) estimate disability costs to be 37.3% and 20.3% of household income, for the severely and the moderately disabled, respectively. These costs translate into 32.7% and 30.3% higher living costs for severely and moderately disabled individuals, respectively, compared to non-disabled individuals in Ireland. For the same country, the Indecon (2004) estimates the additional cost at EUR 143 per week on average for households without an elderly person. For Spain, Pino and Pérez (2011) conclude that the respective costs amount to 72% and 40% of household income. For Cambodia, Palmer et al. (2018) estimate a need for 19% higher income for people with disabilities to reach the same standard of living as their counterparts, ceteris paribus, while for European countries, Morris and Zaidi (2020) give an estimate of 30%. For the US, Morris et al. (2022) estimate the need of an additional 29% in the income of households with disabled members to achieve the same SoL as individuals in households without disability. Mont et al. (2022) estimate that households with disabled members need 6% more income in Ethiopia, 4% in Zimbabwe, and 10% more in Tanzania. In Ghana, Asuman et al. (2021) estimate the presence of a member with a disability in the household translates into a 23.5% decrease in the household’s standard of living compared to a similar household without a member with a disability, while Mont and Cuong (2011) estimate a 11.5% additional cost of living for households with members with disability in Vietnam. In Malaysia, Amin and Adros (2019) find the additional cost of living for households with disabled members to be 23.4% of monthly income. When the sample is split, the estimate becomes 26.7% for rural and 19.6% for urban areas, respectively, while the extra cost for people with no limitations in daily activities is 5.9% of monthly income. For the Philippines, according to Carraro et al. (2023), the additional cost of having a child with a disability ranges from 40% to 80% extra expenditure, depending on the severity of the disability, compared to households without members with disability.

The standard of living is controlled for using several proxies, mainly material possessions: material hardship, food insecurity, and ability to meet essential expenses (She and Livermore 2007); home ownership (Cullinan et al. 2013; Antón et al. 2016); ownership of other “goods”; ability to take vacation (Cullinan et al. 2013); difficulty households face in making ends meet; and ownership and access to assets (Antón et al. 2016). Other measures include an asset index including 322 items which is further analyzed based on PCA tetrachoric analysis (Mont et al. 2022), food and non-food items (Asuman et al. 2021), and a combination of housing characteristics3 and assets4 (Carraro et al. 2023). Mont and Cuong (2011) and Amin and Adros (2019), unlike most other studies, use income to proxy for standards of living.

Existing studies employing the SoL method are limited to the UK (Zaidi and Burchardt 2005; Morciano et al. 2015), US (Morris et al. 2022; She and Livermore 2007; Jones and O’Donnell 1995), China (Loyalka et al. 2014), Ireland (Indecon 2004; Cullinan et al. 2011; Cullinan et al. 2013), Cambodia (Palmer et al. 2018), Spain (Pino and Pérez 2011), Vietnam (Minh et al. 2015), the EU (Antón et al. 2016; Morris and Zaidi 2020); sub-Saharan Africa, including Ethiopia, Tanzania, Liberia, Nigeria, Namibia, Zimbabwe, and Malawi (Mont et al. 2022); Ghana (Asuman et al. 2021; Vietrnam (Mont and Cuong 2011); Malaysia (Amin and Adros 2019); the Philippines (Carraro et al. 2023); and Tamil Nadu state in India (Center for Inclusive Policy 2024), highlighting the need to expand geographical coverage to reach more general conclusions.

3.1.4. The Budget Standards Approach

The Budget Standards Approach records the goods and services needed, in a particular place at a particular time, to attain a certain standard of living for an individual with disability. Fiscal models start with the proposition that it is the consumption of goods and services that determines living standards. This approach involves identifying the specific goods and services necessary to achieve a certain standard of living and then costing them (Saunders et al. 1998). The advantages of this approach, as identified by Amin and Adros (2019), are that costs can be accurately assessed and verified, and that this method assesses specific disability-related needs rather than spending patterns, that are usually dependent on the income factor. However, Smith et al. (2004) highlight the fact that the Budget Standards Approach is built on the premise of an existing consensus regarding a minimum acceptable standard of living. According to Smith et al. (2004), the priced lists of items necessary to guarantee a minimum standard of living should be compiled by the people with disabilities themselves, as they are best placed to know the needs and priorities associated with disability.

3.1.5. Studies Following Mixed Methods

In addition to studies following the structured methods listed above, some studies use a combination of methods in an attempt to offer more comprehensive and less method-specific results. These studies are listed as “mixed methods studies”. Wilkinson-Meyers et al. (2010) present an innovative method for calculating the additional living costs of persons with disabilities. With this mixed methodology, they try to identify additional resources and costs related to disability. The mixed methodology they use is an integration of a social disability framework model and a financial cost model using a budget standards approach in order to identify the additional support, equipment, travel, and time needed to enable people with disabilities to live an “ordinary life” in the community. Surveys are then used to validate their findings as well as to identify gaps in information and community resource priorities. They succeeded with the methodology they used to integrate a social model of disability with economic principles to identify additional disability-related resources. As a result, they present both the needs related to impairment and the resources needed due to the experience of impairment in the disability society, ultimately producing a comprehensive list of disability-related resources calculated by people with disabilities, with the aim of reducing and removing social and environmental barriers and achieving an adequate standard of living in the community. Finally, the most important achievement of this method is the integration of the social and economic impact of the opportunity cost of time.

Mixed methods are also used by Mont (2023), who adopt the Goods and Services Required (GSR) method, drawing on the expertise of people with disabilities, parents of children with disabilities, and service providers to arrive at a detailed description of the type and extent of specific goods and services required by people with different types of disabilities and the level of support needs. However, Mont (2023) makes no estimation attempt but limits the scope of the study in providing the existing theoretical frameworks.

In the Center for Inclusive Policy (2024) study report, focusing on the state of Tamil Nadu, India, the disability policy implemented is based on the medical model of disability. The CIP report examines the structure and extent of the extra costs incurred by people with disabilities in order to ensure their equal participation in society. Using the method of Goods and Services Required (GSR), the CIP report estimates the additional costs based on direct costs related to disability. In addition, they survey expert groups and focus groups and categorized expenditures by type for participation in education, transport, entertainment, community, and participation in decision-making. The CIP study finds that people with disabilities belong to low- and middle-income households. The additional costs due to disability were estimated to be 3 to 6 times more than family income for people with low support requirements and 2 to 10 times more for those with high5 support requirements. Also, the report suggests that the government could provide up to 30% of the required goods and services for people with disabilities. In addition, the families of persons with disabilities undertake the coverage of the majority of the necessary goods and services for their members with disabilities.

3.2. The Reasons for Difficulty in Measuring/Estimating Costs

Measuring the extra costs borne by people with disabilities is made difficult by the fact that not correctly estimating them and not including all the factors affecting the extra costs can distort their correct depiction and may lead to an underestimation of the additional costs borne by persons with disabilities. In addition, each method that tries to estimate the extra living costs of people with disabilities faces some problems in the process of calculation.

Tibble (2005) argues that the reasons that make it difficult to measure/estimate costs are the following:

• Measuring realized or potential expenses: in several studies respondents answer what they actually spend, which in fact is not what they would like to spend if they had sufficient resources. This is because expenditure is limited by the income available to the individual and is influenced by the preferences/decisions of their budget. People with disabilities may not have sufficient income to cover additional costs that would ensure them the same standard of living as a person without disabilities who has the same income. Moreover, these people are unlikely to cut their non-disability-related costs enough to cover the potential costs of their disability, because there is a minimum expenditure on certain items that each person needs simply to survive. Therefore, measuring the actual costs incurred by people with disabilities will result in an underestimation of the cost of fully meeting the needs of a person with disabilities.
• Imperfect knowledge: studies that ask respondents about their expenses are subject to errors due to a lack of knowledge of the respondent. Respondents may find it difficult to know how much they are spending at the moment, as well as how much they would spend on everyday items if they had not been confronted with disability.
• Opportunity cost: people with disabilities are often faced with shorter life expectancy and are thus more likely to prefer to consume today than tomorrow. Therefore, their preferences for saving are different. As a result, their opportunity costs are not taken into account in the estimates.

Additional Problems related to the Standard of Living and Standard Budgets Approaches:

The problems associated with standard of living approaches are (Tibble 2005):

• It assumes that people spend first on disability-related needs and then on indicators of living standards, whereas in fact they are likely to spend on both types of needs at the same time. Therefore, this method does not measure the extent to which disability-related needs are met.
• By calculating how much more a person with a disability must receive to achieve the same standard of living as a person without a disability, ceteris paribus, we essentially measure the realized additional costs rather than the potential costs. In essence, this method is a measure of how tight people have to make their financial budget.
• The benefits should be “reversible means of testing”, that is, giving more money to those with higher incomes, which is clearly not practical.
• The needs of households affected by disability cannot be considered to be met simply by providing extra income to achieve the same standard of living as households that do not have members with disabilities.

Mont et al. (2022) argue that the SoL method is an important tool for estimating the average additional costs of people with disabilities. However, it has the following limitations:

• It takes into account only the direct expenditure of households and thus does not take into account the indirect costs of disability, i.e., the loss of income.
• Disability-related costs may not be significant in low-income countries because many people face a high-income restriction and are more likely to be unaware of or have access to goods and services needed to participate.

The approach to standard budgets has the following problems (Tibble 2005):

• Until now, budget standards for people without disabilities in similar conditions have not been developed. Therefore, there is no control group.
• Services provided free of charge or at a subsidized rate by statutory or voluntary organizations have not been adequately received from the budgetary point of view.

According to Wood and Grant (2010), the standard budgeting method faces the following weaknesses:

• The lack of a model ‘control’ budget for people without disabilities makes it difficult to determine how estimated costs differ from those of people with disabilities.
• The default standard of living on which costs will be based is ambitious and highly subjective.

4. Conclusions

The existing literature estimating the additional costs of people with disabilities is still scarce, despite its relatively long existence. The main disadvantage pertains to the difficulty in the estimation, in conjunction with the burden caused by the unavailability of data, which demotivates further researchers from aiming to improve the existing methods and reaching more informative conclusions. Several methods have been introduced in the literature; however, none of them have proven to be both more accurate and more practically useful to policymakers.

At the moment, existing studies have focused mainly on EU and Anglo-Saxon countries, in addition to some sub-Saharan countries, Malaysia, the Philippines, Ghana, Vietnam, Cambodia, one state in India, and China. This limited geographical coverage provides certain estimates for a group of countries, while leaving behind more than 75% of the countries worldwide.

Our survey provides the existing theoretical framework within which disability has been defined, the different theoretical models of disability, the methods for estimating the additional costs of living for people with disabilities along with the main advantages and disadvantages of each one, and the findings pertaining to these costs. Finally, it assesses the difficulties related to assessing/estimating these costs.

The main conclusions drawn from the present survey point to significant additional costs of living for people with disabilities, depending on the type and intensity of disability, which in all cases are not less than 20% of household income, while increasing significantly depending on the specifics.

The great mix of definitions, models, estimation methods, and findings provides sufficient evidence that the research topic under investigation is tremendously complicated. In addition, the urgent need for scientifically based evidence to help formulate public policies which address the needs of individuals with disabilities and their families is a practical matter of undoubtful importance. Thus, the present study offers directions for further research, in an attempt to identify solutions to existing problems and specific answers to practical matters.

5. Future Directions

In order for policy makers to design policies which accurately address the needs of people with disabilities, adjusting their standard of living to the level of individuals without disabilities, ceteris paribus, several issues need to be addressed.

First, statistical agencies should focus on collecting data with adequate information on disability type and size, in addition to details regarding income, expenditures, and expenditures specific to disability, with sample sizes adequate enough to produce robust statistical results. Surveys should be designed by national statistical agencies in ways that they conform so that statistical analyses can be made in a comparative way. Data should be representative of the local population, and surveys should be performed periodically rather than with discontinuity. All of the above will allow for cross-country and cross-time analyses and comparisons.

Second, geographical coverage should be expanded, following the requirement of data availability, in order to be able to assess the existing situation in the rest of the countries around the world. At the moment, studies are very limited in terms of their geographical scope and are often not generalizable even within the countries they are conducted (see, for example, the study of CIP, which is only specific to the state of Tamil Nadu in India, and the study of Amin and Adros (2019), that examines the additional cost based exclusively on data drawn from a university employee sample). Public policy formation requires evidence which is not sample-specific and is based on a representative sample.

Last, researchers should further elaborate on the existing methods in order for estimates to become more accurate, uniform, and applicable to different types and levels of disability, regardless of the geographical characteristics and the idiosyncrasies of country-level public policies. Although the SoL method, dominant in the literature, provides quite specific estimates depending on the type and the severity of disability, it is seen to have large ranges with regard to the estimates provided. Wide range estimates are not easily interpreted when it comes to policy formation. The existing literature shows that mixed methods, although more complicated and more time consuming when adopted, could offer further insights into the quantitative estimates of the SoL through more direct and specific questions to individuals and other experts. Thus, scientists should delve further into the methodological approaches in an attempt to suggest a mixed method which, when accompanied by the necessary justification, can provide more accurate estimates of the disability-related expenses.