The Impact of Introducing Brokerage Type ISA on the Breadth of Minority Shareholders

This study empirically investigates the impact of the Brokerage Type Individual Savings Account (ISA), introduced in 2021, on the distribution of minority shareholders in publicly listed firms in South Korea. The ISA is a tax－advantaged financial product that allows investors to manage various financial instruments within a single account, offering tax exemptions on net gains. Initially launched in 2016, the Brokerage Type ISA —a version that permits direct investment in domestic stocks — was newly introduced in 2021.

Using firm－level panel data from 2011 to 2023, this study examines whether the introduction of the Brokerage Type ISA contributed to the expansion of minority shareholder distribution. The empirical results show a significant increase in the distribution of minority shareholders following the implementation of the Brokerage Type ISA. Notably, the expansion was more pronounced among stable firms characterized by higher dividend payout ratios and older firm age, rather than high－growth firms.

This suggests that the structural features of the ISA —such as the mandatory holding period and tax exemption limits —may have encouraged long term investment and a preference for stability among retail investors. Furthermore, the findings indicate that the implementation of the Brokerage Type ISA contributed to enhancing firm value through the diversification of minority shareholder ownership. This study makes a novel contribution as the first empirical evidence showing that the ISA system not only increases retail investment participation, but also influences corporate governance, firm valuation, and the structure of capital markets.

It also offers meaningful policy implications for future discussions on expanding the investment base of retail investors and promoting firm value.