Information content of sustainability index recomposition: A synthetic portfolio approach
研究了公司被纳入或剔除道琼斯可持续性指数（DJSI）对股票收益的影响，发现纳入有显著正向公告前效应和持续异常收益，剔除也有正向收益但后期显著性降低，且对非标普500公司信息作用更强。
A firm’s inclusion on the Dow Jones Sustainability Index (DJSI) signals its leadership in Environmental, Social, and Governance (ESG). We studied the effects of DJSI inclusion using data through 2021. For additions, we found significant positive pre-announcement effects, as well as persistence of positive abnormal returns. On deletions, we also saw positive abnormal returns, although significance reduced in later years. Our analysis demonstrated a stronger information role of DJSI inclusion for non-S&P 500 firms, which suggests that the DJSI is relatively more important for firms with lower investor recognition. We used a generalised synthetic control approach to estimate our results, which responds to the parallel trends critique of stock return event studies and provides robustness to industry shocks that are so important to ESG applications. Thus, this paper represents an important extension to our understanding of the value relevance of DJSI membership.