社外取締役増員は企業パフォーマンスに影響を及ぼすのか

The Companies Act requires listed companies to have at least one outside director. The law requires that outside directors be independent of any person who has been executing the business of the company at the time of their appointment and for 10 years prior to their appointment. In addition, Tokyo Stock Exchange (abbreviated as “TSE”) ensures the effectiveness of its Corporate Governance Code (abbreviated as “CG Code”), which is included in the appendix to the Securities Listing Regulations, and which came into effect in June 2015, was revised in June 2018, and was most recently revised for the second time in June 2021 to reflect the reorganization of TSE market. Although the CG code is based on a comply-or-explain approach, it is indirectly subject to pressure from investors. Among the most recent revisions, Principle 4-8, “effective use of independent outside directors” has attributed attention, finally requiring as a principle of action that Prime market of TSE listed companies should appoint at least one-third or more independent outside directors who are fully qualified in certain respects. From now on, this increase in the number of outside directors is expected to raise the presence of outside directors and is expected to cause no small change in the composition of the board of directors. Although it can be predicted that the supervisory and executive functions of the board of directors will be clearly separated, there is a concern that the rapid increase in the number of outside directors will only be a formal response to this demand. Because the fact that outside directors have not been permeated in Japan to date. Therefore, this study analyzes how the increase in the number of outside directors in a short period of time in anticipation of this revision affects the composition of the board of directors, and how the new composition of the board of directors affects the performance of listed companies. In the most recent revision, it is noted that the composition of the board of directors should incorporate gender diversity and other factors. Regarding gender diversity, the ratio of female board members is still low in Japan, and this is an important issue. Given that the most recent revision calls for both diversities, it can be assumed that the increase in the number of outside directors and the increase in the ratio of female directors are occurring simultaneously in the boards that are currently being reconstituted. The two should complement each other, but in Japan, where the penetration of outside directors has lagged that of other countries, the increase in the number of outside directors and the ratio of female directors may be particularly strongly linked. In this study, we also examined the effect on the ratio of female directors in companies that have at least one-third of their board members as outside directors. The results of the analysis revealed that SA ratio, which represents the assets utilization ratio, declined for firms with at least one-third of outside directors. This means that firms with at least one-third of outside directors have more agency problem and more likely to experience agency problems than others. This suggest the opposite happened rather than governance being strengthened in firms with more than one-third outside directors. Next, regardless of whether the ratio of outside directors is more or less than one-third, the effect on corporate performance can be ignored. This result follows the findings of Matsumoto [2019, pp.77-79], a previous study. Finally, we find that the ratio of female directors is higher in firms where the ratio of outside directors is more than one-third than others. This indicates that both outside directors and female directors are recognized as tools for strengthening governance. One implication of this study, which analyzed data from before the revision of the CG Code in April 2022, clearly showed that the ratio of female directors tended to be higher in companies that had set the ratio of outside directors at one-third or more prior to the revision of the code. In other words, it is expected that in many cases, the establishment of outside directors has been influenced by the recent policy to utilize women along with the revision of the code, and that the establishment of outside directors has been realized by women. In any case, it seems that both the increase in the number of outside directors and the utilization of women are progressing. It will be necessary in the future to examine whether the adoption of outside directors is a mere formality without substance and whether the adoption of outside directors does not affect corporate value in the first place. Finally, we mention the remaining issues. The binomial logistic regression model employed in this study to calculate the Propensity Score of firms with one-third ratio of outside directors needs to be reexamined. In the present study, the model was constructed by only CG coefficients. So, the explanatory power of the analytical model could be enhanced by introducing financial variables, industry indicator, etc. into the model in the future. We would like to further reduce the differences in information background between the two groups through such work, and we would like to revise the model to identity causal effects that could not be found in this analysis. And we need to consider cases such as Principle 4-7 of the CG Code describing “the role of outside directors includes promoting sustainable corporate values”. In other words, since this study was concerned with the analysis method of PSM, we believe that we have responded to such advice to a certain extent by adopting multi-year averages as the dependent variable. However, we have recognized limitations. Although this analysis examined the effect of increasing the number of outside directors in a single year on corporate performance, we would rethink these results by using an average indicator for multiple years rather than a single year. Given the discussion above, these issues remain to be addressed in the future.