Evaluating Corporate Carbon Emissions Reporting: Assessing Transparency and Completeness with the Carbon Integrity Index

Abstract

Corporate carbon emissions reporting is central to climate accountability, yet significant gaps remain in transparency, completeness, and methodological rigor. This study introduces the Carbon Integrity Index (CIX), a structured framework for assessing disclosure quality through ten indicators covering Scopes 1, 2, and 3. Unlike existing standards focused on reporting requirements, the CIX evaluates how well emissions are reported, addressing methodological transparency, scope coverage, and treatment of uncertainty. Applied to 2022 sustainability reports from companies listed in Spain’s IBEX 35 index, the framework reveals an average score of 5.7/10, with 69% of firms achieving passing results. While Scope 2 reporting was generally robust (mean: 0.82), Scope 3 disclosures—often representing the majority of emissions—and uncertainty assessments were systematically weak (mean: 0.08). Findings provide empirical support for legitimacy and institutional theory, showing how formal compliance can mask performative compliance that limits meaningful accountability. Sectoral differences suggest that institutional pressures and operational complexity shape divergent transparency pathways, raising concerns that universal standards may entrench reporting disparities. The CIX offers regulators, investors, and companies a practical tool for distinguishing symbolic from substantive disclosure, enabling more informed decision-making and strengthening the role of reporting in driving the transition to net-zero business models.

1. Introduction

The 21st-century business paradigm is characterized by the convergence of multiple forces that redefine expectations regarding corporate performance and transparency. Regulatory pressure, exerted through increasingly demanding regulatory frameworks; social pressure, manifested in stakeholder demands and public opinion; and financial pressure, reflected in investment decisions based on ESG (Environmental, Social, Governance) criteria, shape a new operational landscape for organizations. The disclosure of climate information and greenhouse gas (GHG) emissions represents a paradigmatic case of this transformation, demonstrating how environmental concerns have evolved from peripheral considerations to become central elements of corporate strategy and accountability.

Climate disclosure began gaining relevance in the 1990s with the introduction of the “triple bottom line” concept, which incorporated economic, social, and environmental factors into business performance assessments [1]. This “integrated thinking” approach defines current frameworks that examine the interplay between organizations and environmental issues. This has been channeled through Integrated Reporting (IR) standards [2], which call for a holistic consideration of all forms of capital (financial, manufactured, intellectual, human, social/relational, and natural) to create sustainable value in the short, medium, and long term.

IR offers advantages such as greater transparency, reduced information asymmetry, improved decision-making, and stronger stakeholder accountability [3,4]. It is more commonly adopted by large, profitable, and sustainability-driven firms, while companies in less competitive sectors often avoid it to protect strategic information [5,6].

However, IR faces challenges including inconsistent standards, limited technological and financial resources, and high implementation costs, especially for Small and Medium-sized Enterprises (SMEs). The lack of global regulatory alignment affects comparability, while its use as a marketing tool can lead to greenwashing, reducing credibility and stakeholder trust.

In this context, carbon accounting represents a fundamental tool for companies to operationalize their climate commitments and transition toward net-zero business models. Quantifying, tracking, and reporting direct and indirect GHG emissions across corporate operations provides the foundation for regulatory compliance and the development of science-based decarbonization strategies. However, emerging literature highlights that framework effectiveness depends critically on data quality and methodological rigor [7,8]. Ensuring transparency in these processes is vital for both internal governance and the credibility of sustainability reporting. While carbon accounting shapes strategic decision-making and sustainability trajectories, its credibility requires robust assurance systems and accountability models capable of validating that reported progress reflects genuine movement toward zero-carbon systems.

One of the most widely accepted standards for carbon emissions reporting is the GHG Protocol [9], which classifies emissions into three categories: Scope 1 (direct emissions from owned or controlled sources), Scope 2 (indirect emissions from purchased electricity), and Scope 3 (all other indirect emissions across the value chain). While this classification provides a comprehensive theoretical framework, its practical application reveals significant inconsistencies that compromise the goal of complete carbon accounting. The uneven treatment of Scope 3 emissions represents a particularly critical challenge to corporate accountability theory, as these emissions typically constitute the majority of an organization’s carbon footprint [10] yet remain systematically underreported or excluded from corporate disclosures.

This inconsistency is institutionalized through regulatory frameworks that perpetuate incomplete reporting. Under the Science Based Targets Initiative (SBTi) Corporate Net-Zero Standard guidelines, Scope 3 reporting is only required when it constitutes more than 40% of total emissions [11], creating a paradoxical situation where the most material emissions may be legally omitted. Similarly, Spanish regulations mandate Scope 1 and 2 reporting while Scope 3 accounting remains optional for private companies [12], illustrating how regulatory fragmentation undermines the comprehensive accountability required by sustainable business models.

Currently, multiple international reporting frameworks require companies to disclose their environmental impact. Yet, their transformative potential is severely limited by the lack of methodological, technical, and organizational transparency. Opacity in calculation models, poor data traceability, and diverse sectoral criteria prevent establishing a common basis for evaluating climate commitment effectiveness. As a result, confidence in reported metrics declines, intersectoral comparisons become unfeasible, and rigorous monitoring toward net-zero is impaired.

Given the absence of a binding global standard, it is imperative that all reporting frameworks adopt rigorous methodological transparency principles. Only through this convergence can divergences between standards be identified, the rigor of reduction plans be evaluated, and genuine progress toward climate objectives be verified. Transparency becomes a functional requirement for corporate climate governance [13,14]. It is not just a matter of disclosing what is reported, but how.

To address the gap between emissions metrics and credible net-zero strategies, this study introduces the Carbon Integrity Index (CIX), a structured evaluation framework that quantitatively assesses the transparency, accuracy, and comprehensiveness of corporate carbon footprint reports. While existing frameworks focus on reporting requirements, the CIX provides a systematic methodology for evaluating disclosure quality, bridging the gap between formal compliance and substantive accountability.

The CIX’s conceptual contribution lies in its ability to transform qualitative assessment into quantitative evaluation, enabling systematic comparison of reporting quality across organizations and sectors. By applying ten specific indicators across all emission scopes, the framework addresses scope coverage and methodological transparency gaps left unresolved by current approaches. This approach aligns with calls in the sustainable business literature for rigorous measurement systems that can distinguish between genuine sustainability efforts and symbolic actions.

The application of this framework to Spanish IBEX 35 companies provides an empirical foundation for understanding how large corporations navigate the tension between disclosure requirements and methodological rigor. This case study serves both as a practical demonstration of the CIX methodology and as a contribution to understanding sectoral variations in reporting quality, along with the drivers and barriers to transparent carbon accounting.

2. Carbon Emissions Reporting Framework

Corporate carbon emissions reporting operates within a diverse ecosystem of global frameworks, each with a distinct focus and scope. Among the most widely recognized programs are the Global Reporting Initiative (GRI), the Carbon Disclosure Project (CDP), the Task Force on Climate-Related Financial Disclosures (TFCD), and the recent European Sustainability Reporting Standards (ESRS), specifically ESRS E1 on climate change. While they aim to enhance transparency and comparability in corporate carbon accounting, significant challenges remain in achieving true standardization and coherence [15,16]. This complex landscape reflects underlying theoretical tensions about the purpose of disclosure and its effectiveness in driving meaningful corporate transformation toward net-zero business models. A comparison of these key frameworks is presented in

Table 1. Comparison of GRI 305 [17], ESRS E1 [18], CDP [19], and TCFD [20].

Criteria	GRI 305	ESRS E1	CDP	TCFD
Scope of reporting	GHG emissions (Scope 1, 2, 3)	GHG emissions, reduction targets, risks/opportunities	Climate data, emissions, corporate strategy	Climate-related financial risks and governance
Regulatory status	Voluntary	Mandatory in the EU	Voluntary but widely used	Voluntary, with growing regulatory adoption
Focus	Transparency and comparability	Comprehensive climate disclosure	Corporate climate action	Financial risk disclosure
Emissions coverage	Scope 1, 2, 3	Scope 1, 2, 3 (mandatory)	Scope 1, 2, 3 (encouraged)	Scope 1, 2 (Scope 3 when relevant)
Alignment with GHG Protocol	Yes	Yes	Yes	Encourages alignment
Sector-specific guidance	General, but allows sector adaptation	Yes (specific to various industries)	Yes, but focuses on climate strategy	No, applies to all sectors
Materiality approach	Single materiality (Impact on environment)	Double materiality (Financial + Environmental impact)	Primarily environmental	Primarily financial
Stakeholder focus	General public and regulators	Regulators, investors, stakeholders	Investors, stakeholders, supply chains	Investors, financial institutions
Use for investment decisions	Moderate	High	High	Very high

.

These frameworks share a common foundation, encouraging or requiring the disclosure of GHG emissions across Scopes 1, 2, and 3, often referencing the GHG Protocol as a methodological basis. Their shared overarching goal is to increase transparency for stakeholders, including investors, regulators, and civil society [21]. However, two principal points of divergence stand out: their respective legal enforceability and their underlying conceptions of materiality [22].

2.1. Mandatory vs. Voluntary Frameworks

A primary tension exists between voluntary regimes (GRI, CDP, TCFD) and mandatory ones (ESRS). While voluntary programs offer benefits in stakeholder engagement, mandatory disclosures are seen as having greater potential to improve data quality and comparability [15,23]:

• Voluntary frameworks (GRI, CDP, TCFD) have been pivotal in building awareness and creating a market for climate disclosure, particularly CDP and TCFD in financial markets. However, their voluntary nature can result in inconsistent application, selective disclosure, and “greenwashing,” where reporting serves legitimacy purposes rather than driving internal change [24].
• Mandatory framework (ESRS E1): The introduction of ESRS E1 under the EU’s Corporate Sustainability Reporting Directive (CSRD) marks a significant shift by making detailed disclosure of Scopes 1, 2, and 3 mandatory for a large number of companies, aiming to standardize data and enhance accountability.

This creates regulatory fragmentation across regions, with the coexistence of voluntary and mandatory regimes contributing to reporting heterogeneity [25,26,27]. Companies face difficulties navigating these overlapping frameworks, leading to inefficiencies, while market forces and investor pressure have already pushed for alignment with frameworks like TCFD and CDP [25].

2.2. Financial Risk vs. Double Materiality

A second conceptual gap lies in the different approaches to materiality. This is not merely a technical detail but reflects a fundamental disagreement about the purpose of corporate reporting:

• Financial materiality (TCFD-centric view) prioritizes how climate-related risks and opportunities could affect a company’s financial performance. This “outside-in” perspective, designed primarily for investors and financial institutions, represents a “financialized accounting technology” that constructs climate risk in a way that is legible and manageable for financial markets [28,29].
• Double materiality (ESRS and GRI approach) requires companies to report not only on how sustainability issues affect the business (financial materiality) but also on how the business’s operations impact society and the environment (impact materiality). This “inside-out” perspective provides a more holistic view of corporate responsibilities [30].

A focus solely on financial materiality may lead companies to ignore significant environmental impacts if they are not perceived as an immediate financial risk. Conversely, double materiality pushes for a more integrated strategy where environmental and social responsibilities are embedded in the corporate governance and business model, aligning more closely with the transition to a net-zero economy [30,31].

2.3. From Reporting to Accountability

The transition from descriptive reporting to genuine corporate accountability represents a central challenge in the pursuit of net-zero business models. The proliferation of frameworks such as the GRI and TCFD has increased the volume of climate-related information but also created a complex and fragmented landscape [32]. This diversity shapes not only the structure and content of disclosures but also the organizational behaviors that underpin them, a dynamic explored in the literature through legitimacy theory and institutional theory [8].

As previously mentioned, integrated thinking offers a conceptual bridge between internal strategic processes and external reporting, yet in practice, there is often a marked decoupling from this ideal. Legitimacy theory helps explain this gap: disclosure can become a symbolic act aimed at managing stakeholder perceptions and maintaining a “social license to operate” rather than reflecting substantive change [33]. The existence of multiple, often voluntary, frameworks enables companies to cherry-pick metrics that portray them in the best possible light, thereby securing legitimacy without committing to costly operational transformations toward net-zero [34].

Framework adoption is also shaped by isomorphic pressures (i.e., mechanisms that drive organizations to resemble others in their field) described by institutional theory. For example, the financial sector’s widespread embrace of the TCFD is less a purely market-driven choice than a response to strong institutional demands to “financialize” climate risk [32]. This creates sector norms that compel other firms to adopt similar practices to be seen as credible actors [29]. While such convergence can foster standardization, it may also narrow the scope of reporting to financial materiality, potentially sidelining broader environmental impacts: a key tension when contrasted with the double materiality approach embedded in ESRS and GRI, as previously described.

At its core, accountability differs from disclosure. As research on the zero-carbon transition shows, publishing a report does not equate to being answerable for climate outcomes [33]. Accountability requires verification mechanisms, stakeholder dialogue, and tangible consequences for inaction or misrepresentation. The current reporting ecosystem is weak in these areas: assurance is often voluntary, methodologies for calculating uncertainty lack standardization, and penalties for poor-quality data are rare [29]. Without these safeguards, reporting risks becomes a self-referential exercise, failing to fulfill its primary role as a mechanism to facilitate and enforce the corporate transition to sustainable business models.

In this context, tools such as the CIX can operationalize accountability principles by offering a transparent, standardized, and verifiable measure of GHG emissions reporting quality. This shifts the focus from disclosure volume to disclosure integrity, aligning corporate climate reporting with the substantive requirements of the net-zero transition.

3. Methodology and Data

3.1. Carbon Integrity Index

Existing carbon emissions reporting frameworks provide guidelines for disclosure, but often lack a standardized way to assess the quality and completeness of these reports. Many companies disclose emissions inconsistently, particularly for Scope 3, where methodological gaps and voluntary reporting lead to fragmented data. The presented CIX here addresses this issue by offering a structured evaluation framework that quantifies the transparency, accuracy, and comprehensiveness of carbon footprint reports. Importantly, the CIX aims to be applicable to any type of organization, regardless of its ownership structure (public or private), geographic location, or size.

By applying 10 specific indicators (

Table 2. Carbon Integrity Index (CIX) methodology indicators.

Indicator	Name
CIX1	Activity data for Scopes 1 and 2
CIX2	Emission factors
CIX3	Scope 1
CIX4	Scope 2
CIX5	Scope 3: Purchased goods and services
CIX6	Scope 3: Other upstream activities
CIX7	Scope 3: Waste
CIX8	Scope 3: Other downstream activities
CIX9	Scope 3: Regular mobility of users and employees
CIX10	Uncertainty assessment

) across Scopes 1, 2, and 3, the CIX ensures a more objective and comparable assessment, enabling organizations, investors, and policymakers to gauge the reliability of emissions disclosures beyond mere compliance with existing standards. These indicators reflect the essential building blocks of a rigorous carbon footprint assessment: activity data, emission factors, emissions by scope (usually expressed in CO₂ equivalent units), and uncertainty analysis.

Each indicator is scored on a scale from 0 to 1, using four evaluation levels that reflect the degree of disclosure quality (

Table 3. Weighting of each indicator according to the valuation.

Indicator Evaluation	Weighting
Does not comply	0.0
Partially complies	0.4
Satisfactorily complies	0.8
Fully complies	1.0

). The final CIX score is the sum of the scores obtained for all ten indicators, with a maximum of 10 points. All indicators are equally weighted, as each one captures a distinct and necessary dimension of a complete carbon footprint calculation. However, the structure of the CIX provides greater granularity to Scope 3 emissions, with five dedicated indicators (CIX5 to CIX9). This distribution is designed to encourage and reward organizations that engage in comprehensive Scope 3 reporting, which typically accounts for 90% of an organization’s total carbon footprint [9] and presents a more complex calculation challenge. In several of these indicators, disaggregation by location is explicitly valued, as it not only enhances transparency but also enables more precise and effective design and monitoring of emission reduction plans.

3.1.1. CIX1—Activity Data for Scopes 1 and 2

This indicator assesses the availability and traceability of activity data used in calculating Scope 1 and 2 emissions:

• Does not comply (0.0): Emissions are reported without any activity data included.
• Partially complies (0.4): Some activity data is provided, but it is inconsistent or does not clearly align with the emissions reported. This applies to cases where the company provides information on only a certain type of energy consumption, omitting the rest.
• Satisfactorily complies (0.8): Activity data is presented and corresponds consistently with the emission factors applied, allowing for reasonable traceability. This applies to cases where the company provides information on all energy consumption, and it can be associated with each emission category of Scope 1 and 2.
• Fully complies (1.0): Activity data is disaggregated by activity centers, allowing for high traceability and facilitating more targeted emissions management. In cases where the company operates in different countries, it must specify the number of activity centers in each country and provide a breakdown of energy consumption.

3.1.2. CIX2—Emission Factors

This indicator assesses the transparency and quality of the emission factors used to calculate Scope 1 and 2 emissions.

• Does not comply (0.0): Emissions are reported without any reference to emission factors or their sources.
• Partially complies (0.4): A standard or calculation tool is mentioned (e.g., GHG Protocol, ISO 14064), but the specific emission factors used are not explicitly cited. This case applies when one or more databases are cited but are not unambiguously associated with emission categories.
• Satisfactorily complies (0.8): The standard or tool used is clearly referenced and consistently associated with each activity type, although the specific emission factors themselves are not individually cited. This case applies when each database is unambiguously associated with a specific emission category.
• Fully complies (1.0): The emission factors used are explicitly listed, along with the data source, allowing verification of their geographic, technological, and temporal representativeness.

3.1.3. CIX3—Scope 1

This indicator evaluates the completeness of reported direct (Scope 1) emissions, specifically from the three principal categories: stationary combustion, mobile combustion, and fugitive emissions.

• Does not comply (0.0): Two or three emission categories are missing from the report without justification. This also applies when the company provides a total value of Scope 1 emissions without mentioning any source or category.
• Partially complies (0.4): One of the three categories is not quantified, and no explanation is provided. This also applies when the calculated categories are mentioned, but only the overall result is provided.
• Satisfactorily complies (0.8): All three emission categories are quantified separately, and any omission is explicitly justified.
• Fully complies (1.0): In addition to fulfilling the previous level, emissions are disaggregated by location or activity center, enabling more targeted and effective reduction planning. In cases where the company operates in different countries, it must specify the number of activity centers in each country and provide a breakdown of Scope 1 emission categories.

3.1.4. CIX4—Scope 2

This indicator assesses the completeness of reported Scope 2 emissions (indirect emissions from energy consumption), with special attention to the calculation approach applied (market-based vs. location-based) and the treatment of guarantees of origin where applicable. The supplier’s name is not considered relevant for this evaluation.

• Does not comply (0.0): Scope 2 emissions are not quantified, and no justification is provided.
• Partially complies (0.4): Emissions are calculated using the territorial energy mix, but no justification is given for not using a market-based method. This also applies when the calculation methodology is not specified.
• Satisfactorily complies (0.8): Emissions are quantified using a market-based approach, or guarantee of origin certificates are reported.
• Fully complies (1.0): Emissions are disaggregated by location or activity center, supporting more targeted reduction strategies. In cases where the company operates in different countries, it must specify the number of activity centers in each country and provide a breakdown of Scope 2 emissions.

3.1.5. CIX5—Scope 3: Purchased Goods and Services

This indicator evaluates the reporting of indirect emissions related to the procurement of goods and services, one of the most material categories in Scope 3.

• Does not comply (0.0): Emissions from purchased goods and services are not quantified, and no justification for their omission is provided.
• Partially complies (0.4): These emissions are quantified, but they are not classified into relevant categories, and no justification is given for any exclusions. Additionally, no consumption inventory is provided. It also applies when consumption data that should be reported due to the nature of the company is missing (e.g., when a construction company does not report the consumption of raw materials such as steel and concrete).
• Satisfactorily complies (0.8): The emissions are classified into appropriate categories, and omissions are explicitly justified. It also applies when the company provides an overall result but includes a consumption inventory.
• Fully complies (1.0): Emissions are classified into categories, and a consumption inventory is also provided, enhancing traceability.

3.1.6. CIX6—Scope 3: Other Upstream Activities

This indicator evaluates the reporting of indirect emissions from upstream activities, including capital goods, fuel- and energy-related activities, upstream transportation and distribution, business travel, and leased assets.

• Does not comply (0.0): No upstream activities’ emissions are quantified, and no justification for their omission is provided.
• Partially complies (0.4): Only isolated upstream activities are quantified, without classification or justification for excluding other categories.
• Satisfactorily complies (0.8): Emissions from upstream activities are fully reported by category, and any omissions are explicitly justified.
• Fully complies (1.0): Emissions from upstream activities are fully reported by category, and any omissions are explicitly justified. Additionally, data sources and/or activity data used in the calculation are explicitly referenced, enabling transparent and comprehensive reporting and minimizing subjectivity in the assessment.

3.1.7. CIX7—Scope 3: Waste

This indicator evaluates the reporting of indirect emissions associated with waste management, including conventional, non-conventional, and hazardous waste.

• Does not comply (0.0): No waste-related emissions are quantified, and no justification for their omission is provided, regardless of whether a waste inventory is provided or not.
• Partially complies (0.4): Only certain categories of waste are quantified, without classification or justification for excluding other types. A waste inventory is also not provided.
• Satisfactorily complies (0.8): Emissions from all relevant waste categories are categorized and quantified. This also applies when the company reports the total emissions of this category and additionally provides a waste inventory.
• Fully complies (1.0): Emissions from all relevant waste categories are categorized and quantified, and the company provides a waste inventory by type (i.e., material, hazardous, non-hazardous) or treatment method (e.g., landfill, recycling, reuse).

3.1.8. CIX8—Scope 3: Other Downstream Activities

This indicator evaluates the reporting of indirect emissions from downstream activities, such as downstream transportation and distribution, product processing and use, end-of-life treatment of sold products, leased assets, franchises, and investments.

• Does not comply (0.0): No downstream activity emissions are quantified, and no justification for their omission is provided.
• Partially complies (0.4): Only isolated downstream activities are quantified, without classification or justification for excluding other categories.
• Satisfactorily complies (0.8): Downstream activities are classified according to an appropriate standard, and results are reported or omissions are explicitly justified.
• Fully complies (1.0): Downstream activities are classified according to an appropriate standard, and results are reported or omissions are explicitly justified. Additionally, data sources and/or activity data used in the calculation are explicitly referenced, supporting comprehensive and transparent reporting.

3.1.9. CIX9—Scope 3: Regular Mobility of Users and Employees

This indicator evaluates the reporting of indirect emissions related to regular commuting by employees and users of the organization’s services or facilities.

• Does not comply (0.0): No commuting-related emissions are quantified, and no justification for their omission is provided.
• Partially complies (0.4): Emissions are quantified for only certain groups of employees or users, without justification for excluding others.
• Satisfactorily complies (0.8): Emissions from regular commuting are fully quantified for all relevant user and employee groups. This also applies when the results are supported by a mobility survey.
• Fully complies (1.0): In addition to quantifying the emissions, detailed information is provided about the mobility survey from which the results are derived, allowing for full traceability.

3.1.10. CIX10—Uncertainty Assessment

This indicator evaluates whether the report includes a meaningful uncertainty analysis, which is essential for improving the reliability of emissions quantification.

• Does not comply (0.0): No uncertainty assessment is provided, and no justification for its omission is included.
• Partially complies (0.4): Uncertainty is assessed, but no methodological details are provided. This also applies in cases where uncertainty is evaluated for only some of the activity data or emission factors.
• Satisfactorily complies (0.8): Uncertainty is assessed, and the methodology used is described. This also applies in cases where uncertainty is associated with all the activity data and emission factors used.
• Fully complies (1.0): Uncertainty is assessed, and the methodology used is described. Uncertainty values are reported for each of the emission categories.

3.2. Evaluation Process

Figure 1 illustrates the evaluation process used to determine the CIX score assigned to corporate carbon emissions reporting. The final numerical score is calculated by summing the points awarded across the ten predefined evaluation criteria described in Section 3.1.1. The assessment follows a structured peer-review methodology to enhance accuracy and minimize subjectivity. Initially, two independent evaluators review the organization’s publicly available disclosures and assign a provisional score ranging from 0 to 10. Subsequently, a third expert, acting as an editor, reviews both evaluations to ensure consistency and rigor in the assessment process. To assess the concordance between the two independent evaluators, Spearman’s rank correlation coefficient (ρ) is applied. This coefficient measures the strength and direction of the monotonic relationship between the scores assigned by both evaluators to each company. A high and positive value of ρ (ρ ≥ 0.4) indicates a high degree of agreement in the ranking of companies based on their reporting quality. If the initial evaluations converge, and the Spearman coefficient indicates a high level of concordance, the final CIX score is approved. In cases of divergence, i.e., when the Spearman coefficient is low (ρ < 0.4), three key actions are triggered to reconcile differences before determining the final score:

• Clarification of evaluation criteria: The criteria for each CIX indicator are thoroughly reviewed and discussed to ensure both evaluators have a uniform understanding of what constitutes “Does not comply,” “Partially complies,” “Satisfactorily complies,” or “Fully complies” for each indicator.
• Additional training for evaluators: If gaps in understanding or application of the methodology are identified, specific training is provided to the evaluators, reinforcing the consistent application of CIX criteria.
• Discussion and consensus session: The editor facilitates a meeting between the evaluators to discuss their score differences, analyze points of disagreement based on the clarified criteria, and reach a consensus on the final score for each indicator. This multi-stage validation process, complemented by the quantification of concordance using the Spearman coefficient and the structured resolution of disagreements, mitigates potential biases and enhances the reliability of the evaluation.

Final Carbon Emissions Reporting Score

Qualitative ratings (e.g., A, B+, C−) are familiar, widely used, and easier to compare across different organizations. They also help simplify complex evaluations, making it more accessible for investors, consumers, and policymakers to understand the strengths and weaknesses of corporate carbon disclosures without requiring deep technical expertise.

In this line, CIX’s final carbon emissions reporting score uses a qualitative scoring system (

Table 4. CIX quantitative and qualitative scoring system.

CIX Score (0–10)	Equivalent Grade	Quality Interpretation
9.0–10	A	Exceptional
8.5–8.9	A−	Excellent
8.0–8.4	B+	Very good
7.5–7.9	B	Good
7.0–7.4	B−	Satisfactory
6.5–6.9	C+	Moderate
6.0–6.4	C	Average
5.5–5.9	C−	Below average
5.0–5.4	D+	Weak
4.0–4.9	D	Deficient
0.0–3.9	D−	Very weak

). The grading scale differentiates reports, making it easier to assess gradual improvements in reporting quality while maintaining transparency and comparability.

The 11-grade structure reflects a balance between methodological rigor and practical applicability and is grounded in several years of application and refinement by multiple evaluators using the CIX across diverse corporate reporting contexts. Since CIX evaluations often involve the public identification of assessed companies, it is important to avoid stigmatizing organizations that are still in the early stages of improving their emissions reporting. For this reason, all scores from 0.0 to 3.9 are grouped into a single, broad grade (“D−”), which signals the need for substantial improvement without imposing a reputational penalty.

Another distinctive feature is the wider top tier: the range required to attain the maximum grade (“A”) spans a full point (9.0–10.0), while all other intervals follow 0.4-point steps. This reflects the principle of encouraging companies to aim for ambitious yet realistic goals. Scores of 9.0 or above are rare and already indicate an exceptional level of transparency and methodological robustness. This expanded range avoids making the highest grade appear unattainable and rewards substantial effort toward reporting excellence.

These grading choices are designed to combine interpretability, motivational value, and reputational sensitivity, and may serve as a reference for researchers applying the CIX in different geographical or regulatory contexts.

3.3. Case Study: Spanish IBEX 35 Companies

This study evaluates the publicly available carbon footprint reports of IBEX 35 companies, applying the CIX to assess the quality of their emissions disclosures. The IBEX 35 is a stock market index created in 1992, representing the 35 most liquid companies listed on the Madrid Stock Exchange. Since its inception, the index has served as a key benchmark for the Spanish economy, covering companies from diverse industries.

As of 31 December 2022, the IBEX 35 companies were classified into seven major sectors: Oil & Energy, Basic Materials/Industry/Construction, Consumer Goods, Consumer Services, Financial Services, Technology & Telecommunications, and Real Estate Services. The carbon footprint information used in this study was primarily sourced from Non-Financial Information Statements (EINF) and Sustainability Reports from 2022, which were publicly available on the official websites of each company. In cases where available, the companies’ dedicated carbon footprint reports were also analyzed to ensure a comprehensive evaluation. The complete list of IBEX 35 companies included in this study is provided in

Table A1. IBEX 35 Companies, 2022.

Ticker	Company	Sector	Subsector
ANA	Acciona	Basic Materials, Industry, and Construction	Construction
ANE	Acciona Energía	Oil & Energy	Renewable Energy
ACX	Acerinox	Basic Materials, Industry, and Construction	Minerals, Metals, and Processing
ACS	ACS	Basic Materials, Industry, and Construction	Construction
AENA	Aena	Consumer Services	Transport and Distribution
AMS	Amadeus IT Group	Technology & Telecommunications	Electronics and Software
MTS	ArcelorMittal	Basic Materials, Industry, and Construction	Minerals, Metals, and Processing
SAB	Banco Sabadell	Financial Services	Banks and Savings Banks
SAN	Banco Santander	Financial Services	Banks and Savings Banks
BKT	Bankinter	Financial Services	Banks and Savings Banks
BBVA	BBVA	Financial Services	Banks and Savings Banks
CABK	CaixaBank	Financial Services	Banks and Savings Banks
CLNX	Cellnex Telecom	Technology & Telecommunications	Telecommunications and Others
ENG	Enagás	Oil & Energy	Electricity and Gas
ELE	Endesa	Oil & Energy	Electricity and Gas
FER	Ferrovial	Basic Materials, Industry, and Construction	Construction
FDR	Fluidra	Basic Materials, Industry, and Construction	Engineering and Others
GRF	Grifols	Consumer Goods	Pharmaceutical Products and Biotechnology
IAG	IAG	Consumer Services	Transport and Distribution
IBE	Iberdrola	Oil & Energy	Electricity and Gas
ITX	Inditex	Consumer Goods	Textiles, Clothing, and Footwear
IDR	Indra Sistemas	Technology & Telecommunications	Electronics and Software
COL	Inmobiliaria Colonial	Real Estate Services	REIT (SOCIMI)
LOG	Logista	Consumer Services	Transport and Distribution
MAP	Mapfre	Financial Services	Insurance
MEL	Meliá Hotels International	Consumer Services	Leisure, Tourism, and Hospitality
MRL	Merlin Properties	Real Estate Services	REIT (SOCIMI)
NTGY	Naturgy	Oil & Energy	Electricity and Gas
RED	Red Eléctrica Corporación	Oil & Energy	Electricity and Gas
REP	Repsol	Oil & Energy	Oil
ROVI	Rovi	Consumer Goods	Pharmaceutical Products and Biotechnology
SCYR	Sacyr	Basic Materials, Industry, and Construction	Construction
SIE	Siemens Gamesa	Technology & Telecommunications	Telecommunications and Others
SLR	Solaria Energía y Medio Ambiente	Oil & Energy	Renewable Energy
TEF	Telefónica	Technology & Telecommunications	Telecommunications and Others

.

By applying the CIX Index to these 35 companies, this study aims to assess the transparency, completeness, and methodological robustness of corporate carbon emissions reporting in Spain’s leading businesses. The findings will provide valuable insights into the effectiveness of CIX carbon emissions reporting, identifying areas for improvement and alignment with international standards.

4. Results

The assessment of IBEX 35 companies’ carbon footprint reporting for 2022 using the CIX methodology reveals critical insights that advance theoretical understanding of corporate environmental disclosure behavior and challenge prevailing assumptions about the relationship between regulatory compliance and reporting quality.

4.1. Overall Performance

The CIX evaluation demonstrates a fundamental disconnect between formal compliance and reporting quality. Among the 35 IBEX 35 companies evaluated, 24 companies (69%) achieved a passing score (≥5.0), indicating that while most companies engage in carbon reporting, the quality of these disclosures varies substantially within the same regulatory environment (

Table 5. CIX scores from IBEX 35 companies.

Company	CIX	Equivalent Grade	Position
Acciona	6.8	C+	13
Acciona Energía	6.8	C+	13
Acerinox	6.0	C	17
ACS	4.0	D	28
Aena	5.2	D+	22
Amadeus	2.8	D−	32
ArcelorMittal	2.0	D−	35
Banco Sabadell	4.8	D	26
Banco Santander	3.6	D−	30
Bankinter	8.2	B+	1
BBVA	4.4	D	27
CaixaBank	3.6	D−	31
Cellnex	6.0	C	17
Enagás	6.8	C+	7
Endesa	6.8	C+	7
Ferrovial	7.2	B−	6
Fluidra	6.8	C+	7
Grifols	6.4	C	15
IAG	6.0	C	17
Iberdrola	6.0	C	17
Inditex	6.8	C+	7
Indra	6.4	C	15
Inmobiliaria Colonial	7.8	B	3
Logista	5.2	D+	22
Mapfre	5.2	D+	22
Meliá Hotels International	6.8	C+	7
Merlin Properties	8.0	B+	2
Naturgy	7.6	B	4
Red Eléctrica	7.6	B	4
Repsol	2.8	D−	34
Rovi	4.8	D	25
Sacyr	6.8	C+	7
Siemens Gamesa	6.0	C	17
Solaria	2.8	D−	32
Telefónica	4.0	D	28

).

The average CIX score across all companies was 5.7, with a median score of 6.0. The most common score (mode) was 6.8, highlighting that many companies cluster around the mid-to-high range of reporting quality (Figure 2). However, the results indicate that while most companies comply with basic disclosure requirements, they do not attain a high standard of quality and transparency.

These findings carry important implications for legitimacy theory and the broader literature on voluntary disclosure. The wide dispersion in scores (ranging from 2.0 to 8.2) challenges the assumption that regulatory frameworks necessarily lead to consistent reporting behavior. This variability echoes previous research on disclosure heterogeneity [35], showing that differences in quality persist even when the content disclosed appears formally similar. Such results strengthen the case for shifting from binary compliance checks toward more nuanced, quality-focused evaluation models.

The observed distribution also highlights a notable absence of firms in the highest performance bracket (9.0–10.0), confirming the so-called “quality ceiling” effect previously documented in sustainability reporting studies [36]. The rarity of exceptional disclosures suggests that existing incentives may fall short in promoting best-in-class reporting. This underscores the need for regulatory approaches that actively reward disclosure quality, not just compliance with minimum requirements.

4.2. CIX Ranking

The highest CIX scores were achieved by: Bankinter (8.2), which was the best performer overall, Merlin Properties (8.0), Inmobiliaria Colonial (7.8), Naturgy, and Red Eléctrica (7.6 each). These companies demonstrated strong emissions reporting practices, including clear methodology, Scope 1, 2, and 3 coverage, and transparency in data sources.

Conversely, the lowest scores were recorded by: ArcelorMittal (2.0), which presented the lowest score, Repsol (2.8), Solaria (2.8), and Amadeus (2.8). These companies showed significant gaps in emissions disclosure, particularly in Scope 3 reporting, emission factor transparency, and uncertainty evaluation.

4.3. Performance by Indicators

The indicator-level results in

Table 6. Average rating by the CIX indicator of IBEX 35.

Indicator	Mean	Median	Mode
Activity data for Scopes 1 and 2	0.73	0.8	0.8
Emission factors	0.59	0.4	0.4
Scope 1	0.63	0.8	0.8
Scope 2	0.82	0.8	0.8
Scope 3: Purchased goods and services	0.59	0.8	0.8
Scope 3: Other upstream activities	0.62	0.4	0.4
Scope 3: Waste	0.60	0.8	0.8
Scope 3: Other downstream activities	0.54	0.4	0.8
Scope 3: Regular mobility of users and employees	0.61	0.8	0.8
Uncertainty assessment	0.08	0.0	0.0

reveal systematic patterns that advance understanding of organizational carbon accounting capabilities and highlight critical gaps in current reporting frameworks:

• Strength in Scope 2: The best-performing indicator was the disclosure of Scope 2 emissions (CIX4), with an average score of 0.82. This suggests that regulatory pressure and the relative methodological simplicity of calculating emissions from electricity consumption have been effective. Notably, market-based accounting methods and renewable energy certificates are optional tools under the GHG Protocol. By adopting these methods, this extends previous research on voluntary environmental standards [37] by illustrating how market mechanisms can become institutionalized within corporate reporting practices, even in the absence of a regulatory mandate.
• Scope 3 reporting deficiencies: The variable performance across Scope 3 indicators (ranging from 0.54 to 0.62) provides empirical evidence for persisting organizational boundary theory applications in carbon accounting. Companies demonstrate slightly better performance in Scope 3 categories where they exercise greater control or visibility (CIX9—Employee commuting: 0.61, CIX7—Waste: 0.60) compared to categories requiring extensive supply chain coordination (CIX8—Downstream activities: 0.54). However, the increasing adoption of input–output methodologies, which estimate emissions based on economic transaction data, is progressively enabling companies to report on Scope 3 categories with greater consistency and comparability, even when data access across the supply chain is limited [38].
• Critical weakness in uncertainty: The systematic failure in uncertainty assessment (mean: 0.08, with 83% of companies scoring 0) represents a critical finding for the advancement in carbon reporting. This widespread omission is particularly concerning given that the importance of uncertainty quantification was highlighted more than two decades ago [39] as essential for enhancing the reliability of emissions data and identifying areas where data quality must improve. Even the GHG Protocol’s own guidance emphasizes that assessing inventory uncertainty is a foundational element of credible carbon accounting. The consistent neglect of uncertainty disclosure by Spanish firms signals what can be described as a form of performative compliance.

5. Discussion

5.1. IBEX 35 CIX Score Implications

The evaluation of IBEX 35 companies using the CIX reveals both progress and persistent challenges in corporate carbon footprint reporting in Spain. While the majority of companies achieved a passing score (5.0 or higher), significant gaps remain in Scope 3 emissions disclosure, uncertainty assessments, and methodological transparency. These findings highlight the need for continued improvement in emissions reporting practices, particularly as regulatory frameworks evolve.

The overall average score of 5.7 suggests that IBEX 35 companies are making efforts to improve their emissions reporting. Companies such as Bankinter (8.2), Merlin Properties (8.0), and Inmobiliaria Colonial (7.8) demonstrate best practices in transparency, methodology, and completeness, providing detailed Scope 1, 2, and 3 inventories. These high-scoring companies clearly disclose emission factors, segment their activity data by location, and provide detailed justifications for data exclusions, setting a benchmark for others to follow.

Encouragingly, Scope 2 reporting (CIX4) had the highest level of compliance, with most companies clearly disclosing electricity-related emissions and, in many cases, specifying the use of renewable energy or market-based factors. This suggests a growing awareness of energy sourcing and its climate impact, likely driven by regulatory and investor pressures.

Despite these improvements, Scope 3 reporting remains a critical weakness. Many companies fail to provide comprehensive Scope 3 inventories, particularly for categories such as purchased goods and services, employee commuting, and downstream activities. This omission limits the accuracy of total emissions assessments and reduces comparability across companies and sectors [40]. Additionally, only a few companies justify why certain Scope 3 categories are excluded, highlighting a need for clearer reporting guidelines and stricter enforcement.

The evaluation of uncertainty (CIX10) was the weakest-performing category, with 29 out of 35 companies failing to provide any mention of uncertainty in emissions calculations [39]. Given that uncertainty assessments are crucial for understanding the reliability of emissions data, this represents a significant gap in reporting quality. Without proper uncertainty estimates, stakeholders, including investors, regulators, and consumers, may struggle to assess the credibility of reported emissions reductions and sustainability claims.

5.2. Sectoral Differences in CIX Performance

The CIX evaluation revealed clear differences in reporting performance across sectors, largely explained by structural, regulatory, and methodological factors. Financial services and real estate companies (e.g., Bankinter, Merlin Properties, Inmobiliaria Colonial) consistently achieved the highest scores, while industrial and energy-intensive firms (e.g., ArcelorMittal, Repsol, Solaria) showed significant gaps in transparency and completeness.

The clear sectoral differences observed reinforce the tenets of institutional theory. The high scores in the financial and real estate sectors can be explained by two factors. First, they are subject to greater regulatory and market pressure (e.g., sustainable finance regulations, EU taxonomy, green building certifications), which acts as a powerful isomorphic mechanism, pushing their practices toward a higher standard [41,42]. Second, their direct carbon footprint is operationally less complex, which lowers the technical barriers to high-quality reporting.

Conversely, the low scores of the industrial and energy sectors not only reflect their high operational complexity (process emissions, extensive value chains) but may also indicate “strategic resistance” [43]. For these companies, full transparency could expose inefficiencies or transition risks with direct commercial implications, leading them to adopt a more cautious or even opaque approach to their disclosure [44]. These insights contribute to the broader debate on whether voluntary reporting frameworks can effectively counterbalance strategic business interests in high-impact sectors.

In addition to technical barriers, strategic considerations further constrain transparency. Disclosing granular emissions data can inadvertently expose sensitive information about production processes and operational efficiencies, with potential competitive repercussions [45]. Moreover, many industrial facilities still rely on legacy infrastructure that predates modern carbon accounting tools. Retrofitting these systems demands significant investment and may not be prioritized unless required by regulation.

5.3. Key Actions to Improve Corporate Carbon Reporting

To enhance the integrity and effectiveness of carbon emissions reporting, companies should prioritize several key actions. Firstly, expanding Scope 3 reporting to encompass all relevant emissions categories is essential [46]. This includes providing clear justifications for any exclusions, as comprehensive Scope 3 accounting offers a complete view of a company’s carbon footprint and identifies significant reduction opportunities.

Secondly, enhancing transparency in emission factors and calculation methodologies is crucial. By clearly disclosing the data sources and assumptions used in emissions calculations, companies can improve the comparability and credibility of their reports, enabling stakeholders to make informed assessments.

Incorporating uncertainty assessments into emissions reporting is another vital step. Quantifying uncertainties associated with emissions data and methodologies ensures the credibility of reported figures and highlights areas requiring data quality improvements.

Lastly, segmenting emissions data by location or activity center facilitates targeted reduction strategies. This granularity allows companies to identify specific areas with the highest emissions and implement focused mitigation efforts, thereby enhancing the efficiency of their sustainability initiatives.

By prioritizing these actions, companies can significantly improve the quality and reliability of their carbon emissions reporting, aligning with best practices and regulatory expectations.

5.4. Aligning Existing Carbon Emissions Reporting Frameworks with the CIX

The CIX provides a structured methodology to evaluate the transparency, completeness, and quality of corporate carbon emissions reports. While existing frameworks establish guidelines for emissions reporting, they do not quantitatively assess the reliability and robustness of the disclosed data (

Table 7. Comparison of CIX with existing frameworks.

Aspect	CIX	GRI 305	ESRS E1	CDP	TCFD
Purpose	Evaluate the quality and completeness of emissions reporting	Standardized disclosure of Scope 1, 2, 3 emissions	Regulatory framework for mandatory climate reporting in the EU	Encourage climate action and accountability	Assess climate-related financial risks
Emissions Coverage	Scope 1, 2, 3	Scope 1, 2, 3	Scope 1, 2, 3 (mandatory)	Scope 1, 2, 3 (encouraged)	Scope 1, 2 (Scope 3 when relevant)
Regulatory Status	Voluntary, assessment-based	Voluntary	Mandatory in the EU	Voluntary but widely used	Voluntary, growing regulatory adoption
Sector-Specific Guidance	General, but adaptable	General, allows sector adaptation	Yes (industry-specific guidance)	Yes, but focuses on corporate strategy	No, applies broadly to financial institutions
Stakeholder Focus	Investors, regulators, businesses	General public and regulators	Regulators, investors, stakeholders	Investors, supply chains, stakeholders	Investors and financial institutions
Evaluation Approach	Scoring-based assessment of reporting quality (0–10/A-D- scale)	Descriptive reporting	Compliance-based disclosure	Scored assessment (A–F scale)	Qualitative financial risk analysis

). In other words, they focus on what should be reported, but not on how well it is reported. The CIX addresses this gap by offering a comprehensive framework that evaluates the methodological soundness of emissions disclosures, including clarity of assumptions, transparency of data sources, and justification of methodological choices.

This complementary role is particularly relevant in the current context of increasing skepticism around the credibility of sustainability reporting and growing concerns about greenwashing. Companies may formally comply with current frameworks but still engage in superficial reporting practices that obscure critical assumptions or omit key methodological details. The CIX introduces a meta-evaluation layer that helps distinguish substantive reporting from mere formal compliance, enhancing the interpretability of disclosures and allowing stakeholders (particularly investors and regulators) to better assess the integrity and comparability of reported data. This fosters greater trust and supports more informed decision-making.

Integrating the CIX into existing carbon emissions reporting standards can significantly enhance the quality and transparency of corporate sustainability disclosures to avoid using these reporting frameworks symbolically [47]. The CIX offers a comprehensive assessment of reporting integrity, both quantitative and qualitative, which can enhance the guidelines provided by GRI 305, ESRS E1, CDP, and TCFD.

To achieve this integration, GRI 305 and ESRS E1 could mandate the disclosure of CIX scores alongside emissions data, offering a clear indicator of the reliability and completeness of the reported information. Similarly, CDP could incorporate CIX assessments into its existing platform, enhancing its role as a key disclosure mechanism that helps organizations navigate socio-political expectations and build stakeholder trust [40]. In the context of TCFD, integrating CIX scores would provide financial institutions with a valuable tool to assess the credibility of climate-related financial disclosures, thereby enhancing risk assessment processes.

Aligning the evaluation criteria of existing standards with the CIX’s scoring methodology would foster more consistent benchmarking. Frameworks like ESRS E1, which offer industry-specific guidance, could adopt CIX’s sector-adjusted scoring to ensure that assessments accurately reflect the unique challenges and emission profiles of different industries.

Incorporating CIX assessments can also enhance verification and assurance processes. The CIX’s emphasis on data accuracy and methodological transparency encourages companies to seek third-party validation of their emissions data. This is especially relevant for mandatory standards like ESRS E1, where regulators could leverage CIX scores to identify firms that meet higher thresholds of reporting quality, simplifying compliance monitoring and enforcement. For this reason, the CIX supports the broader convergence toward more unified and rigorous sustainability disclosure models [48].

To support effective implementation, reporting frameworks could partner with the CIX to develop guidance materials, workshops, and training programs, helping companies improve both the technical execution and strategic communication of their disclosures. These joint initiatives can foster capacity building and contribute to addressing persistent gaps in transparency and standardization across corporate emissions reporting [36].

5.5. Methodological Limitations of Materials and Data

The development and application of the CIX present several methodological and data-related constraints that warrant careful consideration for the interpretation of results and future research applications. The first acknowledged limitation derives from the limited temporal and territorial scope of application. The lack of a wider temporal series or geographical sample could possibly veil some underlying tendencies that were missed by this analysis.

The second limitation that is acknowledged lies in the reliance on expert criteria during the revision process. Although the peer review process mitigates this issue, the attribution system from 0 to 1 in order to obtain the final score in each indicator implies a subjective valuation of sorts.

The third limitation that is identified involves the reliance on publicly available information. Although this allows for an exploration of the public availability and transparency of an organization, there is an inherent risk of both missing relevant information due to human error in the search for the company’s uploaded sustainability or emissions reports, as well as a risk of the company having more detailed and complete non-disclosed footprint information.

While this study focused on large Spanish companies within the IBEX 35, acknowledging that SMEs and non-EU companies may face distinct challenges in carbon reporting, it is important to note the ongoing efforts to expand the applicability of CIX. Concurrent evaluations are actively being conducted on SMEs and other public organizations across Spain and internationally. Through these broader assessments, it has been consistently confirmed that the CIX framework is highly adaptable and applicable to a diverse range of organizations, demonstrating its independence from the specific nature or size of the entity being evaluated. This broader validation underscores the robustness and versatility of the CIX as a tool for assessing carbon disclosure.

In order to address such limitations, the following measures are proposed:

• A broadening of the temporal series and geographical scope of the study. Widening the sample will allow for better comparability and cross-regional statistical validation.
• The development of a standardized evaluation rubric and automated evaluation. Both of these actions would considerably reduce the risk of including subjective valuations in the results, both by generating a normative standard by which the evaluations should abide, as well as including a neutral party through machine learning and semi-automated assessment tools, in order to generate a preliminary basis.
• Triangulation with external data sources and access to non-public data. Accessing public documents from state or inter-state authorities could provide an external additional source to the documents the company publicly publishes. In addition, working in specific sectors with the companies and their internal documents, signing non-disclosure agreements, could provide deeper insight into the real state of their carbon footprint disclosures.

6. Conclusions

This study challenges the prevailing assumption that greater corporate climate disclosure automatically leads to improved transparency and accountability. By operationalizing the distinction between symbolic and substantive reporting, the CIX advances legitimacy theory’s insights into strategic disclosure, demonstrating how organizations can satisfy formal requirements while maintaining opacity in key methodological areas. Applied to companies listed in the IBEX 35 index in Spain, the framework reveals a significant disconnect between formal compliance with reporting frameworks and the substantive quality of emissions data, underscoring the need to move beyond volume toward meaningful disclosure. This pattern of performative compliance (marked by selective scope coverage, weak methodological transparency, and incomplete justifications) reveals systemic weaknesses in accountability, particularly in Scope 3 reporting, which often represents the majority of emissions. The near-absence of uncertainty assessment in 83% of cases suggests that many disclosures convey false precision rather than decision-useful information, undermining both the credibility of climate commitments and the functioning of markets reliant on accurate data.

Sectoral differences further illuminate the interaction between isomorphic pressures and operational complexity, showing how institutional contexts shape divergent transparency trajectories. Such disparities raise the risk that universal reporting standards, while promoting comparability in theory, may inadvertently entrench inequality in practice. For policy, especially under the ESRS Directive, these findings argue for coupling mandatory disclosure with quality evaluation mechanisms to prevent the institutionalization of low reporting standards. The CIX provides one such tool, enabling regulators to monitor not only compliance but also the depth and reliability of disclosures.

The implications for financial markets are equally significant: systematic quality variation challenges the assumption that more disclosure inherently improves risk assessment, calling for a shift from quantity-based to quality-focused evaluation. Existing ESG ratings may overlook critical dimensions of accountability, and future research should examine whether higher-quality reporting correlates with actual emissions reductions and test the framework in other regulatory contexts. Ultimately, advancing corporate climate accountability requires embedding quality as the central metric of reporting performance. Tools like the CIX can catalyze this shift, but lasting change depends on sustained commitment from regulators, investors, and companies to treat disclosure as a lever for genuine climate action rather than a procedural formality.