The study was conducted by Shipeng Yan of the University of Hong Kong, Fan Zhang of Bentley University, and Zhengyu Li of the University of Melbourne. Their central question was deceptively simple: does ESG investment genuinely improve the underlying environmental impact of firms, or does pollution simply move elsewhere in the economy? To answer it, the team looked beyond the ESG ratings that have dominated earlier research. According to Yan, earlier studies often used ESG ratings as the main outcome variable, which made sense at the time, but researchers now understand much better both what those ratings capture and what they can miss. That realization motivated the team to look past the metrics and examine what was actually happening to emissions across organizational boundaries.

The scale of ESG investing explains why the answer matters so much. Since the United Nations established the Principles for Responsible Investment initiative in 2006 to popularize the ESG concept, total assets under management by investors who signed the PRI grew from a few hundred billion dollars to more than 100 trillion dollars by 2021. That extraordinary expansion illustrates the leverage these investors could wield to drive social and environmental change. If that leverage is producing real decarbonization, the implications are encouraging. If it is instead encouraging firms to reorganize their supply chains so that pollution disappears from their own reported accounts while continuing to exist upstream, then the promise of ESG investing is being undermined by a subtle form of decoupling.

Establishing causality in this domain is notoriously difficult, because firms that attract ESG investors may differ systematically from those that do not. The researchers addressed this challenge by using investor-level merger and acquisition events as quasi-experimental variations in firm ESG ownership. When an acquisition changes the composition of a firm’s investor base, it creates a shock to ESG ownership that is not obviously driven by the firm’s own environmental trajectory, which helps support a causal interpretation of the relationship between ESG ownership and pollution outsourcing. Using this approach, the team analyzed a global sample of firms covering the period from 2006 to 2019, drawing on greenhouse gas emission data from Trucost.

The results were striking. A firm’s ESG ownership was positively associated with pollution outsourcing to suppliers, meaning that firms with more ESG-minded shareholders were more likely to move emission-intensive production steps into their supply chains. Crucially, the analysis showed that this outsourcing did not result in a decrease in overall carbon emissions once the emissions embedded in purchased inputs were taken into account. In other words, the direct emissions reductions that ESG investors celebrate in their portfolio companies may, in a meaningful set of cases, be an accounting artifact of where pollution is located rather than evidence that less pollution is being produced.

Why does this form of decoupling persist? Yan points to a fundamental information asymmetry. Investors are set up to understand the companies they own, not to audit every tier of a global supply chain, he explains. Even experienced ESG investors may have good information about a focal firm but only fragmented information about its suppliers. To know whether decoupling is happening, they would need supplier-level data on production, emissions, and sourcing relationships, and those data are often incomplete, voluntary, or commercially sensitive. That information gap, Yan argues, is part of what makes this form of decoupling possible in the first place. A firm can satisfy its investors with a clean direct-emissions ledger while the dirtiest stages of production continue, hidden several tiers deep among contractors that no shareholder ever examines directly.

The study does not conclude that ESG investors are powerless against this problem. On the contrary, the researchers identified unique advantages that such investors hold when they attempt to mitigate pollution outsourcing. One pathway runs through technology transfer. Because ESG investors typically hold diversified portfolios, they can act as conduits that allow firms to access green technologies from other portfolio companies, helping them build clean production capacity in-house. If a firm can adopt eco-friendly processes itself, the economic logic of outsourcing pollution-intensive activity weakens, because the firm no longer needs to push dirty work upstream to please its shareholders.

A second pathway runs through the structure of ownership itself. ESG investors often hold shares not only in a focal firm but also in that firm’s suppliers, which extends their influence beyond the legal boundaries of any single company. This cross-holdings position gives them a lever to address corporate decoupling that stems from a lack of will rather than a lack of capability. By engaging simultaneously with buyers and suppliers, an investor can see and shape the emissions profile of an entire value chain in a way that regulators, rating agencies, and individual firms often cannot. The study found evidence that when investors combine technological support with direct oversight of supplier practices, the tendency to outsource pollution becomes reduced.

Yan is careful to frame the policy implication in realistic terms. The solution, he says, is not to expect investors to become procurement specialists, but to combine better value-chain disclosure and data with investor engagement, supplier oversight, and support for green technologies. That framing suggests a division of labor: regulators and standard-setters should improve the mandatory reporting of scope-three and supplier-level emissions so that the information gap closes, while investors use their engagement tools and portfolio connections to push firms toward genuine clean production rather than cosmetic reorganization of supply chains. Neither actor alone appears sufficient to prevent pollution from migrating across organizational boundaries.

The broader lesson of the research is a cautionary one for anyone who reads corporate sustainability numbers at face value. Direct emissions, the metric most visible to investors and the public, can improve even as the total emissions associated with a firm’s products stay flat or worse. As ESG capital continues to grow and as climate disclosure rules tighten around the world, the study suggests that the next frontier of sustainable finance lies beyond the factory gate, in the opaque tiers of global supply chains where pollution can quietly relocate. Whether the trillion-dollar ESG movement can close that gap will help determine if it becomes a genuine private regulator or an unwitting accomplice in the relocation of the world’s carbon problem.

Subject of Research: The effect of ESG investor ownership on corporate pollution outsourcing to suppliers and total supply-chain emissions

Article Title: Study finds ESG investor pressure sometimes causes firms to shift pollution to suppliers

Article References: Study finds ESG investor pressure sometimes causes firms to shift pollution to suppliers. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: ESG investing, pollution outsourcing, supply chain emissions, carbon emissions, Strategic Management Journal, responsible investment, green technology, investor engagement, corporate decoupling, sustainability, supplier oversight, emissions data