Social Sustainability in an Ageing Chinese Society : Towards an Integrative Conceptual Framework

Social sustainability is a relatively underexposed dimension of the sustainability debate. Diversified and discipline-specific study perspectives and the lack of contextualization make it difficult to gain a comprehensive understanding of social sustainability in non-Western societies. In examining the problems facing a rapidly ageing Chinese society, this paper aims to construct an integrative conceptual framework of social sustainability, taking into account the Chinese contextual interpretations and elderly population in particular. This paper proposes an integrative conceptual framework composed of two key contextualized components: well-being and social justice. Well-being, according to Lindenberg, is the ultimate goal of life and is achieved by relevant themes organized in a hierarchical system. Social justice relating to the equal distribution of resources, opportunities, and rights is also significant for the achievement of well-being. Interpretations of social sustainability are explored within Chinese socio-cultural (Confucianism, collectivism), institutional (welfare regime, hukou system), and demographic (population ageing) contexts.


Introduction
Since the publication of the Brundtland Report in 1987, sustainable development has gained a firm place in global policy agendas.To tackle multidimensional problems such as ecological destruction, poverty, and inequity, sustainable development is normally characterized by three pillars: environmental, economic, and social sustainability [1,2].These three pillars are seen as compatible and mutually supportive rather than completely separated [3].However, over the last few decades, sustainability policies and studies have primarily focused on environmental and economic sustainability, leaving social sustainability relatively underexposed [4,5].
Social sustainability has received increasing recognition in the last decade, and a body of literature discussing its conceptualization and operationalization has emerged within different disciplines, such as sociology, psychology, environmental science, and urban planning [1,[3][4][5][6][7][8].In general, social sustainability is seen as the essential qualities or goals of societies for long-term development.These qualities or goals comprise a large set of scientific and policy-relevant themes, such as basic needs satisfaction, well-being, social justice, social cohesion, social capital, participation, employment, income, and safety.However, due to a lack of theorization and of an integrative conceptual framework, our understanding of the concept of social sustainability is still vague and limited [1,4,5,9].Social sustainability cannot be understood without proper contextualization.Although primarily discussed within a Western context, the meaning or focus of social sustainability and its themes may be construed differently in other socio-cultural and institutional contexts.In the Chinese context, the continuing presence of some traditional philosophical ideologies and collectivistic/socialistic ideologies [10,11] might lead to significant differences in the interpretations of well-being, basic needs, social justice, etc., which are the key themes of social sustainability.For instance, Confucianism, the long-standing prevailing philosophical system and moral doctrine in China, emphasizes the cultivation of virtue and maintenance of ethics, and it considers human society family-based rather than individual-based, stressing the role of the collective/group and social relationships rather than individuals.In addition, some unique Chinese institutional inequalities may provide a different angle from which to understand social justice.For instance, hukou (household registration) system, which registers residents and serves as the basis for resource (housing, health care, and educational benefits) allocation and provision of subsidies, has created institutional inequalities between locals and migrants.Yet little research has so far been conducted into the concept of social sustainability in the Chinese context [12,13].
Moreover, to understand the meaning of social sustainability, distinctions should also be made between different population categories.Contextual differences at the macro level (e.g., cultural and institutional) have a conditioning effect on personal resources, preferences, and activities at the micro level.These conditioning effects are also dependent on personal socio-demographic status (e.g., age, stages in the life course, income).For instance, studies show that the pursuit of well-being varies between old and young generations and between rich and poor groups [14][15][16].Today's Chinese society faces many challenges, including a rapidly ageing population (about 16% were aged 60 and above in 2015 which will increase to 35% by 2050) [17], inadequate security and service systems for the elderly, and many well-being and justice problems experienced by elderly people [18,19].Thus, giving attention to social sustainability for the elderly population is clearly warranted.
This paper therefore aims to construct an integrative conceptual framework of social sustainability, taking the Chinese context and elderly population into account.In the next section, the concept of social sustainability and its themes are discussed.Afterwards, we propose our integrative conceptual framework and elaborate on its key components, taking into account the Chinese cultural and institutional context and the elderly population.Conclusions and discussion are put forward in the final section.

Literature Review on Social Sustainability
There is a growing body of literature that attempts to conceptualize and theorize social sustainability from discipline-specific perspectives [1,2,[4][5][6][20][21][22].From a sociological standpoint, for instance, Littig and Griessler [1] suggest that social sustainability is a quality of societies, which is achieved if work and related institutions within a society satisfy an extended set of human needs and fulfill the normative claims of social justice, human dignity, and participation without damaging nature and its reproductive capabilities.From a planning perspective, Woodcraft [21] believes that social sustainability is about people's quality of life, now and in the future, and that it describes the extent to which a neighborhood supports individual and collective well-being.From a political point of view, Sachs [23] sees social sustainability as resting strongly on the basic values of equity and democracy, the latter defined as the effective appropriation of all human rights-political, civil, economic, social, and cultural-by all people.On the premise that social sustainability should be part of a wider framework for sustainability that strives to cope with environmental and climate change risk, Eizenberg and Jabareen [24] propose a comprehensive conceptual framework of social sustainability, which is composed of four interrelated concepts of socially oriented practices: equity, safety, urban form, and eco-prosumption.Due to the complexity and discipline-dependent nature of these definitions, no consensus has yet been reached on the definition of social sustainability [5,21].However, despite differences, there is some overlap in the various definitions of social sustainability.Social sustainability seems to comprise two generally accepted major dimensions.One refers to people's individual needs satisfaction, well-being, and quality of life, while the other concerns distribution as captured by concepts such as social justice and equity.These two generally accepted dimensions are further reflected in the discussions of the key themes of social sustainability (Table 1).For instance, Littig and Griessler [1] propose three key social sustainability themes: satisfaction of basic needs and quality of life (e.g., income, education, housing, health and environment), social justice (e.g., equal distribution of economic goods and opportunities regarding quality of life and social participation), and social coherence (e.g., social integration and involvement).Dempsey et al. [7] identify two overarching concepts at the core of the notion of social sustainability within an urban context: social equity (e.g., equal access to services, facilities and opportunities) and sustainable community (e.g., social interaction or networks, social participation and networks, stability, pride or sense of place and safety and security).Holden [25] proposes a framework with four key themes (equity, inclusion, adaptability, and security) and seven dimensions (playing, engaging, learning, moving, living, working, and sense of place).Dave [26] Amount of living space; health of the inhabitants; community spirit and social interaction; sense of safety; satisfaction with the neighborhood.
Equal access to facilities and amenities.
Åhman [4] Basic needs; education; quality of life; social capital; social cohesion, integration, and diversity; sense of place. Equity.
These social sustainability themes seem to be very discipline-specific and diverse.They vary widely from abstract (e.g., social justice) to concrete (e.g., equal access to amenities), from subjective (e.g., well-being and needs satisfaction) to objective (e.g., income and health), from non-physical (e.g., safety and quality of life) to physical (e.g., decent housing, environmental quality and urban form) [7,24], from individuals (e.g., capacities and activities) to social relations (e.g., social cohesion and social capital), and from substantive (e.g., basic needs) to procedural (e.g., participation and empowerment) [2].These themes, from a chronological perspective, blend traditional social policy areas and principles (e.g., equity and health) with emerging issues (e.g., demographic changes, participation, needs, social capital, the environment, and more recently, happiness, well-being and quality of life) [5,27].However, these discipline-specific and diverse themes have not been integrated into a more comprehensive conceptual framework [5], which makes it difficult to obtain a clear and comprehensive understanding of social sustainability and to unravel the underlying links between social sustainability themes [5].
In addition, little attention has so far been paid to contextual interpretations of social sustainability.The existing social sustainability concepts and themes have primarily been proposed and elaborated within the context of Western and developed societies, such as the UK, Canada, and Australia.There are few studies concerned with the context of developing countries [26,28].Even less literature is available on social sustainability issues in China [12,13], which held 19.1% (1.4 billion) of the whole world's population in 2015.Due to some socio-cultural and institutional differences, the meaning or focus of social sustainability in the Chinese context may not be quite the same as that in the Western context.
For example, studies have shown that Confucianism, which emphasizes the importance of family harmony and social relations, still has a deep impact on Chinese (and many East Asian) perceptions of happiness and well-being [11,29,30].In light of China's rapid population ageing, filial piety as a Confucian moral principle is particularly relevant to elderly people's well-being [31,32].Studies have also shown that, despite undergoing a transition from collectivism to individualism, Chinese society is still largely collectivistic, stressing social norms, goals, and relations, while most Western societies are more individualistic societies, with greater emphasis on individual needs and goals [10,33].In addition, China has some unique institutional systems, such as the hukou system.Due to the constraints of the hukou system, migrants without a local urban hukou are not entitled to full citizenship rights or the benefits enjoyed by locals, which leads to inequality in their living conditions and well-being in big cities [19,34,35].This institutional inequality could broaden our understanding of the existing social justice and equity themes (e.g., income, gender, and racial inequality).Despite the significance of such contextual factors, context has hardly ever been included in conceptual frameworks of social sustainability.

Conceptual Framework of Social Sustainability
As discussed previously, due to diverging study perspectives and discipline-specific criteria, no consensus on the definition of social sustainability has yet been reached.Little has been done to integrate the diverse social sustainability themes and their contextual interpretations into a more comprehensive conceptual framework.In this section, we propose an integrative conceptual framework of social sustainability, comprising two key contextualized components: well-being and social justice.

Conceptual Framework
Among the various themes that reflect the important long-term qualities or goals for individual and societal development, basic needs and social justice/equity have consistently been held as two fundamental components of social sustainability [5].This is consistent with the original definition of sustainable development as "development which meets that needs of the present without compromising the ability of future generations to meet their own needs", in which needs (what are the important goods for people) and social justice/equity (how to distribute important goods between people) are emphasized [36].Most social sustainability themes, we would argue, are subcategories of these two fundamental components.As some of the few scholars who have touched on the links between social sustainability themes, Littig and Griessler [1] argue that the definition of basic needs should be understood in a broader way and should include an extended set of themes to do with shaping and maintaining a good quality of life.Basic needs could then comprise many themes, including food, income, housing, health, a healthy environment and security, as well as education, employment, recreation/leisure, and social relationships [1].Similarly, in their opinion, a broader definition of social justice should include not only the equal distribution of economic and material goods (e.g., income and welfare), but also equal opportunities related to quality of life and social participation (e.g., equal educational opportunities).
Littig and Griessler [1] lays a good foundation for this research.In line with the above discussion, our integrative conceptual framework of social sustainability comprises two key contextualized components: well-being and social justice, which are interrelated with each other (Figure 1).Well-being is proposed instead of basic needs because well-being is a more up-to-date and holistic theme of social sustainability.Well-being is regarded as the highest good and the ultimate goal of human action, and has received increasing attention in the literature [5,27,37,38].Well-being, as a more holistic concept, can be utilized to integrate and organize basic needs and other social sustainability themes.For instance, since well-being is achieved through the fulfillment of various basic needs [39,40], basic needs actually serve as instruments or subcategories of well-being.The specific links between well-being, basic needs, and other social sustainability themes will be discussed in Section 3.2, where we present a comprehensive well-being framework.
global connotations of well-being and social justice are influenced by connotations from different contexts, and vice versa.It should also be noted that the pursuit of social sustainability needs to be grounded in a balanced and responsible human-nature relationship [1,37] without damaging environmental and economic sustainability [3,4] (Figure 1).However, due to the knowledge gaps mentioned earlier, our integrative conceptual framework will mainly focus on the interrelationships and contextual interpretations of the key social sustainability themes, leaving the human-nature relationships for further investigations.Based on this conceptual framework, a working definition of social sustainability can be proposed: social sustainability is the long-term ability of societies to achieve well-being and to equally distribute all the well-being related resources, rights, and opportunities within a specific socio-cultural, institutional, demographic, and geographical context.In the following paragraphs, we elaborate on the key components of our conceptual framework.

Contextualization of Well-Being
Well-being, as the ultimate goal of human action, generally refers to a good life and the associated essential qualities or goals of life.It is mainly conceptualized on the basis of one's cognitive and emotional evaluation of life (e.g., life satisfaction) and feeling (e.g., happiness) [41][42][43], which are linked to a wide range of sub-components.These sub-components vary widely, from subjective concepts (e.g., life and needs satisfaction) to objective conditions (e.g., health and security), from social (e.g., social relationships) to physical aspects (e.g., a healthy environment), and from goals (e.g., happiness and success) to instrumental behaviors and means (e.g., entertainment and socio-economic resources) [39,44,45].These well-being sub-components are largely consistent with the social sustainability themes discussed above.
The most prominent well-being theories are telic, activity, top-down, and bottom-up theories [38,40].Telic theories (e.g., needs theory and goals theory) imply that well-being is gained when some state or endpoint, such as a goal or need, is attained, with special emphasis on the role of needs satisfaction and goal achievement in well-being [40,41].Activity theories, in contrast, state that wellbeing is a by-product of human activities and arises from behavior, such as carrying out hobbies and interacting with good friends, rather than from achieving specific endpoints [39].Bottom-up theories claim that well-being is the accumulation of many happy and positive moments in a person's daily life, whereas top-down theories state that well-being depends on personality, which influences a person's interactions with the outside world [41].Top-down and bottom-up theories also indicate a hierarchical structure of well-being sub-components, ranging from more universal and static factors to more specific and dynamic factors.It should also be noted that the pursuit of social sustainability needs to be grounded in a balanced and responsible human-nature relationship [1,37] without damaging environmental and economic sustainability [3,4] (Figure 1).However, due to the knowledge gaps mentioned earlier, our integrative conceptual framework will mainly focus on the interrelationships and contextual interpretations of the key social sustainability themes, leaving the human-nature relationships for further investigations.Based on this conceptual framework, a working definition of social sustainability can be proposed: social sustainability is the long-term ability of societies to achieve well-being and to equally distribute all the well-being related resources, rights, and opportunities within a specific socio-cultural, institutional, demographic, and geographical context.In the following paragraphs, we elaborate on the key components of our conceptual framework.

Contextualization of Well-Being
Well-being, as the ultimate goal of human action, generally refers to a good life and the associated essential qualities or goals of life.It is mainly conceptualized on the basis of one's cognitive and emotional evaluation of life (e.g., life satisfaction) and feeling (e.g., happiness) [41][42][43], which are linked to a wide range of sub-components.These sub-components vary widely, from subjective concepts (e.g., life and needs satisfaction) to objective conditions (e.g., health and security), from social (e.g., social relationships) to physical aspects (e.g., a healthy environment), and from goals (e.g., happiness and success) to instrumental behaviors and means (e.g., entertainment and socio-economic resources) [39,44,45].These well-being sub-components are largely consistent with the social sustainability themes discussed above.
The most prominent well-being theories are telic, activity, top-down, and bottom-up theories [38,40].Telic theories (e.g., needs theory and goals theory) imply that well-being is gained when some state or endpoint, such as a goal or need, is attained, with special emphasis on the role of needs satisfaction and goal achievement in well-being [40,41].Activity theories, in contrast, state that well-being is a by-product of human activities and arises from behavior, such as carrying out hobbies and interacting with good friends, rather than from achieving specific endpoints [39].Bottom-up theories claim that well-being is the accumulation of many happy and positive moments in a person's daily life, whereas top-down theories state that well-being depends on personality, which influences a person's interactions with the outside world [41].Top-down and bottom-up theories also indicate a hierarchical structure of well-being sub-components, ranging from more universal and static factors to more specific and dynamic factors.
Attempts have been made to combine these diverse and discipline-specific perspectives into a more integrative theoretical framework.Lindenberg's SPF (Social Production Functions) theory, as one prominent attempt, integrates concepts such as well-being, goals, needs, activities, and resources into a hierarchical framework [40,[46][47][48].According to SPF theory, people strive to improve their well-being or subjective well-being by optimizing two universal goals: physical well-being and social well-being (Table 2).These two universal goals can be attained by means of five instrumental goals or basic needs: comfort and stimulation for physical well-being; and status, behavioral confirmation, and affection for social well-being [47].These five basic needs can be met in turn by lower level activities and resources.By connecting well-being with needs, activities and resources, Lindenberg's well-being theory serves as a comprehensive and cross-disciplinary framework for social sustainability.[40] and van Bruggen [48].
Regarding the needs for physical well-being, comfort needs correspond to the inner drive to reduce the tension of somatic and psychological states such as hunger, thirst, fatigue, pain, and fear [40].They are fulfilled and 'produced' by activities such as eating, drinking, sleeping, and seeking personal safety and property security.Comfort needs and their relevant activities can be fulfilled by well-being resources at the lowest level, such as financial means, food, housing, and physical health.These activities and well-being resources relate to a large group of social sustainability themes, such as income, poverty, housing, health, security, and a healthy and safe urban environment.In contrast to the tension reduction sought by comfort needs, stimulation needs refer to the drives towards arousal, including mental and sensory stimulation [40].Stimulation needs can be fulfilled by physically and mentally invigorating activities such as sports, study, creative activities, and active recreation.These activities require well-being resources such as physical and mental health and financial means.These activities and resources are related to social sustainability themes such as income, health, leisure, urbanity, and a vibrant public realm [7,22].
Concerning the needs for social well-being, status needs refer to a person's relative rank in society, which is mainly based on control over scarce resources such as political power and social and economic capital [49].Status needs can be fulfilled through activities such as paid work, consumption, and excellent performance in a valued field such as arts or sports.This entails lower-level resources such as education, social origin and scarce capabilities.These activities and resources relate to social sustainability themes such as employment, education, and training, and individual or human capacity.Behavioral confirmation needs, similar to social approval, refer to confirmation of doing the right thing, having the right thoughts, and conforming to the right norms in the eyes of relevant others [49].They can be fulfilled by behaviors that comply with external and internal norms, and by resources such as social skills, social networks, and a normative environment.These activities and resources are associated with many social sustainability themes, including social capital, network, capacity and cohesion, social infrastructure, trust, and a sense of community and belonging.Finally, affection needs refer to the need for feelings of love and caring between people in close relationships.Activities such as exchanging emotional support and spending time together can satisfy affection needs.The resources for affection needs include attractiveness, empathy, and intimate ties, with a partner and children for instance.Relevant social sustainability themes include social cohesion, capital, and capacity at the family level.
Lindenberg's SPF theory provides us with a more integrative framework for understanding the interrelationships between various social sustainability themes.As indicated, social sustainability themes should not simply be considered independent goals or qualities.Instead, most of the well-being related themes are interrelated in a hierarchical multi-branch system of social production functions, serving simultaneously as the specific goals of life (e.g., income, health, housing, and social network) and also as instruments of higher level goals.Ultimately, these social sustainability themes function together to achieve the highest goal, subjective well-being.
However, the existing Western literature has paid little attention to contextual interpretations of well-being, especially in Chinese society.While Chinese society is becoming increasingly modernized and globalized, Confucian values and a collectivistic culture are still important in today's China [50,51].Confucianism, as a philosophical system and moral doctrine, asserts that a good life should include not merely material goods, but, more importantly, intrinsic goods such as virtue.Continuously learning and practicing the Confucian virtues of ren (humanity) can help people to reach the highest good (called zhi-shan) [29].Ren means to love humans.The term ren evokes courtesy, unselfishness, and empathy or an intuitive sense of the feelings of others.Ren is practised in real life by applying specific moral principles to five distinctive natural relationships (guanxi): parent/child (qin, affection), sovereign/subject (yi, righteousness), husband/wife (bie, function), older/younger (xu, order), and friend/friend (xin, fidelity) [29,32].Three of the five basic relationships are familial relations; Confucianism considers human society family-based rather than individual-based.In relation to Lindenberg's SPF theory, Confucianism puts a special emphasis on the social aspects of well-being, and as a consequence would prioritize social well-being over personal physical well-being.To achieve social well-being, the satisfaction of affection needs within the extended family seems to be especially important.
Similar opinions are expressed in several studies of collectivism.Studies in the 1980s showed that Chinese society was characterized by a collectivist culture, emphasizing the role of the collective/group and social relationships rather than individuals [52,53].Nevis [53] developed a Chinese version of the needs hierarchy during the socialist period, in which social belonging was considered more fundamental than individual physiological, safety, and self-actualization needs [53,54].Since economic reform in the 1980s, China has experienced a transition from planned to market economy, in which individual efforts and needs and individualistic culture have become increasingly relevant [33].However, Chinese society is still considered a relatively collectivist society [55], with a greater emphasis on social well-being and needs (e.g., behavioral confirmation) than in western societies.
A rapidly ageing population experiences dramatic demographic change and social challenges.It is another contextual factor that influences interpretations of well-being in Chinese society.This context requires special attention for a better understanding of the well-being and needs of Chinese elderly people.Human needs and developmental goals are dynamic and structured by a multitude of factors such as biological maturation and ageing, societal age grading (e.g., going to school, working and retired), institutions, and social norms in the life course [56].Elderly people in the later stages of the life course tend to have different pursuits with regard to their basic needs and well-being.According to Lindenberg and his colleagues, elderly people experience age-related changes in the availability of resources and the possibilities for needs satisfaction and well-being realization [16,57,58].Losses in well-being resources (e.g., health and income) will increasingly outweigh gains during the ageing process.Therefore, substitution of resources and basic needs becomes a crucial adaptive mechanism to delay and mitigate the impact of losses [16].For example, status, mainly attained through occupational prestige, becomes difficult to maintain after retirement.Hence, a common substitution strategy is to put more effort and resources into behavioral confirmation (e.g., more social interaction and activities) and affection needs (e.g., more contact with families and friends) in order to maintain the overall level of social well-being.Comfort, stimulation, behavioral confirmation and affection are also likely to decline gradually with increasing age and declining health, mobility, social networks, and familial resources (e.g., loss of older family members).Elderly people have to apply adaptive strategies to their available well-being resources in order to maintain their overall well-being.Accordingly, for the well-being of Chinese elderly people, it is important to emphasize those themes that are most closely related to their essential but declining well-being resources, such as health, a healthy and safe environment, social networks, and familial networks.In particular, Chinese elderly people probably embrace more traditional values and the Confucian and collectivist culture [31,32].Hence, Chinese elderly people tend to pursue social well-being and social needs more strongly than younger people, especially family-centered affection needs.

Contextualization of Social Justice
While well-being concerns the goods that are important for a good life, social justice deals with how to distribute these goods among people.One of the most influential social justice theories, Rawls' Theory of Justice [59] proposes a general conception of justice: "all social values-liberty and opportunity, income and wealth, and the bases of self-respect-are to be distributed equally unless an unequal distribution of any, or all, of these values is to everyone's advantage".Two principles are highlighted in this theory [59].The first principle stresses a democratic basis of liberties, in that "each person is to have an equal right to the most extensive total system of equal basic liberties compatible with a similar system of liberties for all".The second principle stresses a solution for inequality: "social and economic inequalities are to be arranged so that they are both: (a) to the greatest benefit of the least advantaged, consistent with the just savings principle, and (b) attached to offices and positions open to all under conditions of fair equality of opportunity".In general, Rawls' conception of social justice indicates that, theoretically, all the well-being related resources (e.g., income and wealth), opportunities (e.g., positions) and rights (e.g., liberty) should be equally distributed among people.Under unequal conditions, attention should be paid to improving the well-being of disadvantaged groups (e.g., poor people, physically disadvantaged elderly people).Such a broad conception of social justice in fact covers many existing social sustainability themes, including equity, income equality, equal access to services and opportunities, empowerment, participation, and democracy.
Interpretations of social justice are also influenced by context, in particular the institutional context.According to the so-called Welfare Diamond, the institutional system consists of four actors, who define the connotation of social justice, design the mechanisms for fair distribution, and share the responsibility for welfare provision: the state (via collective and public solidarity), the market (via purchased welfare), the voluntary sector/community (via collective support in communities), and the family (via the reciprocity of kin) [60,61].Different societies emphasize the significance and roles of the four actors differently, leading to different types of political regimes.According to Esping-Andersen, there are three types of welfare state regime: liberal, conservative, and social-democratic [62].
The liberal welfare state regime, which can be found in the US, highlights the importance of the free market and emphasizes equity in the sense of equal opportunity and individualistic equity [62,63].Equal opportunity means equal access to social positions, while individual equity implies that people themselves are responsible for their own welfare, which is to be obtained from the free market rather than the state according to their efforts and contributions.The state only guarantees the basic needs of the worst off by income redistribution.In contrast, the conservative welfare state regime, which can be found in Germany and France, emphasizes the welfare responsibility of both the state and market.It accentuates the equity within the same social hierarchy in light of class and status [63].As a consequence, the social hierarchy is preserved and emphasized due to its functional importance, and the redistribution of welfare is more horizontal than vertical, occurring mainly within the same socio-economic class.In contrast to both of these, the social-democratic welfare state regime, which can be found in Scandinavian countries, stresses the key role of the state and espouses the ideal of egalitarianism, which pursues equity in terms of equality of outcome [63,64].The state takes full responsibility for welfare provision to guarantee a minimum standard of living which is relatively high compared to the other types of regime.
Despite having a welfare regime that is not yet fully established, China conforms more closely to the conservative model, stressing both the state and the market's welfare responsibility [65].Since the establishment of the People's Republic of China in 1949, Chinese interpretations of social justice have undergone several transformations, along with tremendous changes in its political philosophy and institutional system.Influenced by Marxist ideology and the political system of the Soviet Union, Mao promoted a principle of social justice similar to egalitarianism within a state-directed socialist economy and centralized government.The state provided comprehensive welfare packages to workers through danwei (work units), which refers to state-owned enterprises, state agencies, government departments, and other public organizations.Despite the later transition from an equal supply system to a hierarchical salary system, socio-economic inequality within the society was insignificant.In the post-Mao era, in order to promote economic efficiency, Deng decided to reform the planned economy and abandon egalitarianism, and started to support a market economy and equity principles, so that people could be rewarded according to their performance [66].Deng believed that a more egalitarian society could only be built on the foundation of a highly developed economy through "permitting some of the people to become wealthy first" at the primary socialist stage, although it would cause social inequality.Meanwhile, with the decentralization of decision making, local governments gradually were granted more power to guide economic development.However, the market-oriented economy had brought China increasing economic inequity.Later on in 2005, facing the widening economic inequity, the Chinese government proclaimed the concept of "harmonious society", emphasizing the need for more redistribution and equality and aiming at the equalization of basic social services [11,67].In today's China, the responsibility for welfare provision does not rely primarily on the market (liberal) or the state (social-democratic), but on both.Social justice in the Chinese context seems to entail both state-led equal welfare distribution and market-led equal opportunities.
However, access to state-provided welfare is not fully universal or equal.Due to a unique Chinese institutional system (the hukou system), migrants are largely excluded from the welfare and opportunities that local urban residents can enjoy (e.g., housing welfare, social insurance, and education opportunities), resulting in local-migrant inequality in cities [68,69].Introduced in the 1950s, the hukou system aimed to restrict rural-urban migration and maintain social order in the cities.Individuals had to be registered and remain in only one place of regular residence, holding either a local urban or a local rural hukou.Different hukou statuses, however, are associated with different rights and welfare provisions.Consequently, hukou system divides the Chinese population into a favored sector with full citizenship rights (urban residents with a local urban hukou), and a marginal sector with fewer and more transient rights (rural population with a local rural hukou) [70].Since the 1980s, the rigid hukou system has gradually been relaxed to encourage migration and to facilitate economic growth, resulting in a massive influx of migrants into megacities like Shanghai and Beijing.However, except for the few wealthy and well-educated migrants, the great majority of migrants are not granted local urban hukou rights [71].This has led to a new form of inequality, not between urban and rural areas but within megacities.
In addition to the institutional context, the Chinese socio-cultural context also has certain implications for interpretations of social justice.According to Confucianism, social justice should prioritize the pursuits of intrinsic goods and virtues (over material goods), harmonious interpersonal relationships (over individualistic equality) and relational obligations (over individual rights) [29].Influenced by these ideas, the Chinese welfare system is also characterized by collectivism and a strong reliance on family bonds [72], accentuating the relational obligations and welfare responsibilities of the family and friends/acquaintances with close interpersonal connections (guanxi), and autonomy of the family [29,51].For instance, with today's high housing prices in big Chinese cities, young couples cannot usually afford to buy a house on their own at the beginning.It is quite common for their parents to support them financially, to pay a down payment in part or full, or even the full cost [73]; this functions as family-provided housing welfare resulting from familial obligation.To maintain harmony in their broader social networks, Chinese people also tend to express positive emotion (renqing) for friends and acquaintances by caring for their welfare/well-being [51].In the Chinese context, therefore, attention should be paid to the role of the family (and close social relations) as well as the state and market in distributing welfare and influencing Chinese interpretations of social justice.
The issue of social justice is especially relevant for the elderly population in Chinese society.Firstly, elderly people generally experience a decline in their health condition, physical capabilities, and mobility, and become physically more disadvantaged.The inadequate security and service system for elderly people in China [18] also contributes to making elderly people vulnerable and disadvantaged.According to Rawls' social justice principles [59], attention should be paid particularly to such disadvantaged people.Secondly, the institutional inequality caused by the hukou system also affects the elderly population, creating an inequality between the local and migrant elderly people in big cities.Without a local urban hukou, elderly migrants are largely excluded from the local social welfare and security systems, including medical and endowment insurance.Taking medical insurance as an example, elderly migrants usually have to pay their own medical costs or go through a very complicated reimbursement procedure.In view of elderly people's increasing need for health care, this institutional inequality makes the lives of elderly migrants in cities more difficult.This institutional inequality is also reflected in geographical space, creating socio-spatial differentiations and residential segregation between locals and migrants in cities [70,[74][75][76].Recent studies show that elderly migrants in Shanghai are concentrated in the dilapidated areas of the central city and at the urban periphery, while the locals dominate the city center [14,19].This socio-spatial inequality leads to unequal spatial accessibility to various well-being-related urban services and amenities, such as hospitals, parks and markets.Lastly, the Chinese socio-cultural context also has significant implications for interpretations of social justice for elderly people.The Confucian virtue of filial piety (to love, respect, and support one's parents and ancestors) emphasizes the relational obligations of children towards their parents and grandparents.Thus, it is considered righteous and just for children to provide family-based long-term care, physical assistance, and financial and emotional support to their elderly parents [31,32].Due to housing shortages and the government's inadequate provision of care for the elderly in cities, many families still choose to live with their older parents to fulfil the relational obligations for eldercare [50].

Conclusions and Discussion
Social sustainability is still a relatively underexposed and undertheorized dimension of the sustainability debate.Diverging study perspectives and discipline-specific definitions make it hard to obtain a comprehensive understanding of social sustainability.In addition, the lack of contextualization limits our understanding and interpretation of social sustainability for non-Western societies and for different population categories.This paper aimed to construct an integrative conceptual framework of social sustainability, taking Chinese contextual interpretations and the ageing Chinese population specifically into account.
This paper proposes an integrative conceptual framework of social sustainability comprising two key contextualized components: well-being and social justice.Well-being and social justice correspond to the goods that are important for a good individual life, and the fair distribution of these goods among people.Context refers to all the socio-cultural, institutional, demographic, and geographic contexts that influence interpretations of well-being and social justice.This paper employs Lindenberg's theory of social production functions to integrate various well-being related social sustainability themes into a hierarchical multi-branch framework, and Rawls' theory of social justice to integrate themes relating to the equal distribution of all the resources, opportunities, and rights of importance for the production of well-being.
In addition, this paper also explores the interpretations of social sustainability within the Chinese socio-cultural (e.g., Confucianism, collectivism), institutional (e.g., welfare regime, hukou system), and demographic (e.g., population ageing) context.It shows that, influenced by Confucian and collectivist culture, Chinese people, especially the elderly, tend to prioritize social well-being and needs, particularly family-centered affection needs, over physical well-being and needs.Unlike younger people, the elderly generally experience a decline in well-being resources (e.g., health, social, and familial networks) and face increasing challenges to maintain their overall well-being.Within the Chinese institutional and socio-cultural context, the meaning of social justice seems to include state-led equal welfare distribution, market-led equal opportunities, and family-led welfare responsibility.State-provided welfare is not yet equally accessible to migrants due to the hukou system, resulting in an inequity between locals and migrants (including the older sub-categories) in cities.The family also plays an important role in the welfare distribution for elderly people, influenced by the Confucian virtue of filial piety.
This paper contributes to a more comprehensive and systematic understanding of social sustainability by constructing an integrative conceptual framework.This paper shows that Lindenberg's well-being theory could be an appropriate cross-disciplinary framework for researchers to use to integrate various well-being related social sustainability themes, varying from basic needs satisfaction to activities (e.g., employment, leisure, and socialization) and resources (e.g., health, financial means and social networks).This potential could be further increased by incorporating a more sophisticated interpretation of well-being-related activities and resources based on the emphases of specific disciplines.For instance, planners and geographers could attempt to incorporate more spatial and geographical well-being resources into this framework, such as leisure facilities, social spaces, and a healthy and safe environment.
By examining the Chinese context and the situation of the elderly population, this paper shows the importance of contextual interpretations.As a next step, it would be interesting to focus on social sustainability for the elderly and for disadvantaged elderly migrants in Chinese cities, and to investigate how specific contextual factors influence their well-being and the distributive equality of well-being resources.Distributive equality can include non-spatial (e.g., income and medical insurance) but also spatial and geographical resources (e.g., amenities and facilities) and refer to issues such as spatial equality, accessibility, and socio-spatial differentiation and segregation.Further research could also investigate and compare the meanings of social sustainability in different contexts (e.g., socio-cultural, institutional and geographical) and for different population categories (e.g., younger adults, youth, and ethnic groups).It is also important to realize that contemporary societies, including Chinese society, are becoming more and more diversified and complex, and many subcultures exist in each society.As China integrates more Western attitudes towards well-being and justice (e.g., materialization), the younger generations will tend to act and think differently from older generations.Future research could focus on the meaning of social sustainability across various subcultures and generations.

Table 1 .
Examples of key themes of social sustainability.
Source: Adapted from Ormel et al.