스튜어드십 코드의 도입이 피투자기업의 ESG에 미치는 영향-DID(Difference in Differences) 방법을 중심으로

This study analyzes the impact of institutional investors participating in stewardship codes on the ESG activities of their investee companies. We examine whether stewardship code–compliant institutional investors, who possess both the incentive and the ability to monitor the managers of investee firms, can influence the ESG activities of those firms. The study conducts an empirical analysis using firm-year samples of KOSPI and KOSDAQ companies from 2013, before the introduction of stewardship, to 2023, after its adoption, covering a 11-year period. The variables indicating whether an institutional investor joined the stewardship code during the target year (treated) and whether they invested in a portfolio company after the introduction of the stewardship code (post) were constructed by manually matching the Korea Corporate Governance Service’s stewardship code membership records with the list of the top five shareholders of the portfolio companies. Through this process, variables that can directly influence the decision-making of portfolio companies were created for all institutional investors, including the National Pension Service, and this generalization and manual matching represent a significant difference from prior research. Additionally, compared to multiple regression analysis, the difference-in-differences (DID) method, which can mitigate issues caused by omitted control variables and directly explain the effects of policy introduction, was used, and the parallel trends test, a key assumption of DID analysis, was performed. It was confirmed that investors who joined the stewardship code can have a significant influence on the ESG decision-making of portfolio companies, positively impacting the detailed aspects of E (environment), S (social), and G (governance). Additionally, to address the possibility of sample selection bias, propensity score matching (PSM) analysis was additionally conducted. To review the confounding effects caused by prolonging the introduction period in the effect analysis of the policy introduction, the sample period was reduced. In both additional analyses, the results were found to be generally robust. The regression analysis on the change in ESG scores of the investee firms with Stewardship Code–signatory institutional investors shows that the adoption of the Stewardship Code positively influenced the changes in the total ESG score (ΔESG_T), as well as the environmental (ΔE) and social (ΔS) dimensions of the treated firms, while no significant effect was found in the governance dimension (ΔG). The significance of this study lies in generalizing the analysis to stewardship code–participating institutional investors rather than specific institutional investors such as the National Pension Service. It analyzes the impact of stewardship code–participating investors on portfolio companies’ corporate social responsibility activities and employs difference-in-differences(DID) analysis to examine the causal effect of the policy introduction.