Do Higher-Rated or Enhancing ESG of Firms Enhance Their Long–Term Sustainability? Evidence from Market Returns in Korea

In this study, we investigate the effects of the level and changes in environmental, social and corporate governance (ESG) rating, an index developed to represent a firm’s long-term sustainability, on the stock market returns of Korea Composite Stock Price Index (KOSPI) listed firms over the period 2011–2018. We find that the changes in ESG ratings have statistically significant short-term effects on their abnormal returns. However, their impacts on short-term abnormal returns decrease some days after the disclosure and become negative in the third year. The results imply that investors in the Korean stock market do not view corporate social responsibility activities as a means of supporting their long-term sustainability, judging from the firm value for a long period after their rating. Rather, based on the effects of the changes on coefficient signs over the period—positive in the year and the year after, no effects in the following year, and negative in the third year and later—we can infer that the short-term oriented market sentiments of investors might worsen their long-term stock performances, thus deteriorating their sustainability and growth opportunities.