Impact Investing in NSE-Listed ESG Indices: Abnormal Returns, Calendar Effects, and GARCH-Based Volatility Dynamics in the Indian Stock Market

This study examines the risk–return performance of Nifty100 ESG and the Nifty Enhanced ESG equity indices listed on India’s National Stock Exchange (NSE) relative to the conventional Nifty 100 benchmark from April 2011 to June 2023. Rather than asserting formal “abnormal returns” in the asset-pricing sense as per CAPM or multi-factor alpha estimation, this study documents systematic return outperformance and time-varying volatility dynamics using unit root tests, month-of-the-year dummy regressions with ARIMA error correction, and GARCH-family conditional volatility models. The two ESG indices delivered cumulative returns much higher than the broader Nifty 100 index. Conditional volatility peaked for ESG indices when compared to Nifty 100 during the April 2020 COVID-19 shock, indicating marginally greater ESG resilience. A distinct March effect, which is analogous to the January effect in developed markets, is observed to be significant for the ESG indices. Our findings underscore the growing importance of responsible investing and time-varying risk premia in the Indian equity market.