Production-based emission accounts attribute CO2 to the territory where goods are produced; consumption-based accounts, computed with global multi-regional input–output (MRIO) models, attribute emissions to the country of final consumption. Testing the Environmental Kuznets Curve (EKC) hypothesis — an inverted-U relationship between per-capita income and emissions — on consumption-based emissions, Dong, Wang and Guo (2016) found, for 189 countries over 1990–2012 using the Eora MRIO database, that the inverted-U EKC does not exist: consumption-based CO2 rises approximately linearly with income, implying that production-based inverted-U evidence partly reflects carbon displaced through international trade. Their conclusion rests on consumption-based accounts whose measurement reliability and normative status remain contested. The open problem is to establish the shape of the global income–consumption-based CO2 relationship robustly — across MRIO databases and their quantified uncertainties, allowing for technology heterogeneity of traded goods and for carbon embodied in entrepôt re-exports — and to construct a formally specified hybrid allocation of producer and consumer responsibility under which the shape conclusion is stable. Later literature has advanced every ingredient (technology-adjusted accounting, uncertainty quantification, improved MRIO and Chinese emission data, continued panel testing) but has not settled either the empirical shape question or the responsibility-allocation question.

Background

The Environmental Kuznets Curve (EKC) hypothesis posits an inverted-U-shaped relationship between per-capita income and environmental degradation: emissions rise during early industrialization and fall once income passes a turning point, by analogy with Kuznets's classic curve for income inequality. For CO2 emissions the evidence is notoriously mixed, and a long-standing concern is that territorial production-based accounting (PBA) — the convention of the UNFCCC and the Kyoto Protocol, which counts emissions where they physically occur — may mislead in an economy organized through global supply chains. A substantial share of the CO2 emitted in emerging economies is embodied in exports consumed elsewhere: Davis and Caldeira (2010) computed that in 2004 about 23% of global CO2 emissions were traded internationally, and Peters et al. (2011) showed that net emission transfers from developing to developed countries grew from 0.4 to 1.6 Gt CO2 between 1990 and 2008, exceeding the emission reductions required by the Kyoto Protocol. If rich countries offshore emission-intensive production while continuing to consume its output, production-based inventories can show a spurious improvement — the phenomenon of carbon leakage.

The alternative is consumption-based accounting (CBA): using a multi-regional input–output (MRIO) model — a global input–output table linking all countries' sectors, whose Leontief inverse (the standard input–output matrix inverse that traces direct and indirect production requirements) attributes each unit of final demand to the production, and hence the emissions, it draws on anywhere along the supply chain — emissions are reallocated to the country of final consumption. Global MRIO databases such as Eora (Lenzen et al. 2013) made such calculations possible for a near-complete country set. Dong, Wang and Guo (2016) used Eora, covering 189 countries over 1990–2012, to compute consumption-based CO2 and estimate EKC-type panel regressions (fixed- and random-effects models, dynamic panel GMM — a generalized method of moments estimator suited to panels with a lagged dependent variable — and heterogeneous estimators such as the common correlated effects mean group estimator, which allows country-specific slopes and controls for cross-sectional dependence driven by common shocks). Their headline result: the inverted-U EKC does not exist for consumption-based emissions — consumption-based CO2 rises approximately linearly with income — while production-based estimates display curves whose implied turning points lie far outside observed income ranges. The apparent production-based EKC thus partly reflects carbon displaced through trade, not a genuine decoupling of consumption from emissions.

The authors' concluding discussion lists the challenges that keep that conclusion provisional. First, consumption-based accounting faces data constraints: sector-level MRIO tables carry little information about the technologies used to produce imported products, goods that are imported, processed, and re-exported through entrepôt trade (trade routed through intermediary hubs such as Hong Kong or the Netherlands that re-export goods after little or no processing) are hard to trace, and feedback loops in intermediate-goods trade complicate the calculations. Second, the weighting between producer and consumer responsibility is an open normative and analytical question — a full consumer-pays principle is one pole of a family of allocations, and no agreed principle fixes the weights. Third, implementing consumption-based obligations in territorially based treaties faces institutional hurdles. Fourth, the rapidly growing embedded emissions of emerging economies such as China need tracking, MRIO data resolution and timeliness need improvement, and feasible hybrid accounting frameworks blending production- and consumption-based principles need to be designed.

The surrounding literature frames these challenges. Kander et al. (2015) proposed technology-adjusted consumption-based accounting, which reallocates emissions when a country's export sectors are cleaner or dirtier than the world sectoral average, precisely to address the unknown-import-technology problem; a published exchange (Domingos et al. 2016, with the reply of Kander et al. 2016) shows this correction is itself contested. Lenzen et al. (2007) formalized shared producer–consumer responsibility, in which each agent along the supply chain bears a fraction of each emission proportional to its value-added share. Steininger et al. (2016) argued that no single accounting system is best for all policy purposes and proposed instead the consistent compilation of multiple carbon accounts. Rodrigues et al. (2018) quantified the uncertainty of consumption-based carbon accounts across five MRIO databases. Policy-oriented reviews (Afionis et al. 2017; Tukker et al. 2020) document that the technical complexity, mitigation effectiveness, and political acceptability of consumption-based approaches remain unresolved. On the empirical side, the CO2 EKC literature remains inconclusive overall (Shahbaz and Sinha 2019), and studies continue to test the EKC for consumption-based emissions (Khan et al. 2020; Makarov and Alataş 2024).

Problem Statement

Dong, Wang and Guo (2016) established, subject to the limitations of consumption-based accounting, that the global relationship between per-capita income and consumption-based CO2 emissions is approximately linear — no consumption-based Environmental Kuznets Curve exists — implying that production-based inverted-U evidence partly reflects carbon displaced through international trade. The open problem, still live in the literature, has one overarching objective: determine the true shape of the global income–consumption-based CO2 relationship, and make that determination robust by resolving the accounting choices on which it depends. It comprises two interrelated objectives: (1) establish the shape of the relationship between per-capita income and consumption-based CO2 emissions for a broad global panel — in particular, whether the approximately linear relationship obtained with a single MRIO database is robust or gives way to a curve with turning points — in a way that is robust across independent MRIO databases and their quantified uncertainties, across estimator classes that handle cross-sectional dependence and slope heterogeneity, and with the treatment of unobserved import technologies and of carbon embodied in entrepôt re-exports made explicit; and (2) construct a formally specified hybrid allocation that blends producer and consumer responsibility — well-defined on any MRIO table, preserving the global emission total, and reducing to pure production-based accounting and pure consumption-based accounting at boundary values of the weighting parameter — and show whether the shape conclusion from (1) is stable across the weighting family. The two objectives are scientifically linked: the shape determination depends on the accounting convention under which emissions are attributed, while a hybrid allocation whose consequences for the shape question are unexamined would remain an unexercised formalism; together they bear on whether economic growth alone ever decouples consumption-driven carbon emissions at the global scale. The institutional strand of the source's outlook — whether territorially based treaties could adopt consumption-based or hybrid obligations — is context and motivation, not part of the scientifically evaluable claim.

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