Introduction

Environmental externalities, such as pollution and climate change, impose substantial economic costs on the global economy. This research investigates whether making local environmental risk more salient can induce financial markets to better incorporate these risks into firm valuations. The study focuses on financial analysts, whose assessments of future cash flows significantly influence stock prices. The authors examine whether heightened pollution salience changes analysts’ assessments of regulatory and demand-related environmental risks, subsequently affecting their expectations of firms’ future earnings and value.

Context

The study exploits the large-scale expansion of China’s ambient air pollution monitoring network, which began in 2012. This nationwide network of monitoring stations reported real-time concentrations of six major air pollutants: fine particulate matter (PM2.5), coarse particulate matter (PM10), ozone (O3), carbon monoxide (CO), nitrogen dioxide (NO2), and sulfur dioxide (SO2), alongside a composite Air Quality Index (AQI). Prior to 2012, data collection was often subject to manipulation by local bureaus. The new program installed more than 1,600 EPA-grade stations across 337 cities, providing public access to hourly pollution levels via the internet and mobile applications.

Empirical strategy

The research employs a stacked-cohort difference-in-differences (DiD) design, taking advantage of the staggered rollout of monitoring stations across different cities at different times. The analysis compares changes in an analyst’s output before and after monitoring was introduced in their city of residence, relative to other analysts covering the same firm at the same time but residing in cities where monitoring had not yet been introduced. This within-firm-time comparison holds constant firm-specific fundamentals and common information. The final sample includes 39,950 analyst reports issued by 715 unique analysts covering 1,460 unique firms between 2010 and 2015.

Analyst discussions of air pollution

The findings indicate that following the introduction of monitoring in their city, analysts became more than twice as likely to discuss air pollution in their research reports. This represents a 2.2 percentage point increase, approximately 105% relative to the pre-treatment mean. Placebo tests regarding unrelated social topics, such as human capital, showed no corresponding increase, suggesting the effect is specific to pollution salience. Analysts primarily increased their discussion of transition risks, specifically regulatory risks (94% increase) and preference-related factors (81% increase), rather than physical risks or stakeholder responses. The discussion of both current and anticipated future regulatory developments saw significant increases.

Impacts on firm stock prices and their persistence

Changes in analyst attention are reflected in market valuations. Using an LLM-based classification to categorise firms as green, brown, or neutral, the study finds that reports issued by treated analysts generated more negative market reactions for brown firms and more positive reactions for green firms. Specifically, the three-day cumulative abnormal return was 1.185 percentage points more negative for brown firms and 0.834 percentage points more positive for green firms. These price responses do not subsequently reverse over the following year, indicating that environmental risks became durably incorporated into stock prices. A back-of-the-envelope calculation suggests cumulative market-value gains of approximately $35 billion for green firms and losses of $139 billion for brown firms, totalling approximately 5% of China’s total stock market capitalisation in 2011.

Mechanisms

Heightened pollution salience induced analysts to engage in greater information acquisition. Treated analysts became approximately four times as likely to visit green firms and 2.5 times as likely to visit brown firms via corporate site visits. Furthermore, treated analysts issued more accurate earnings forecasts following the introduction of monitoring, particularly for firms where environmental risks are most financially material. For brown firms, analysts issued more pessimistic earnings forecasts (7.8% lower), lower target prices (9.9% lower), and weaker stock recommendations (3.8% lower). Conversely, for green firms, earnings forecasts increased by 6.4%, recommendations by 3.5%, and target prices by 11.4%.

Conclusion

The research demonstrates that ambient environmental monitoring can affect asset prices by making environmental risks more salient to sophisticated intermediaries. By inducing greater information production and improving the timeliness of price discovery, public information policies can facilitate the pricing of environmental risk even without direct regulation of emissions or mandatory disclosure obligations. The evidence suggests that the effects of information provision depend not only on availability but also on whether it attracts the attention of market participants and motivates them to investigate cash-flow implications.