This study investigates the impact of introducing the equal allocation method(EAM) for public offering stocks on individual investor participation and stock prices. The study aimed to determine whether the EAM expanded individual investor involvement and how it affected stock prices compared to the previous proportional allocation method. The introduction of the EAM increased the number of shareholders participating in public offerings. This increase in participation could either enhance the efficiency of stock prices by attracting more informed investors or exacerbate speculative trading, leading to higher market excess returns. To assess the effects, the study employed event study and Cahart four-factor analysis to measure excess returns before and after the EAM. The findings indicate a decrease in cumulative excess returns of public offering stocks after the introduction of the EAM. The study also found that the excess return (alpha value) of public offering stocks decreased after the introduction of the EAM, suggesting improved stock price efficiency. Overall, the study highlights the importance of increasing market participation through the EAM and enhancing the efficiency of public offering stock prices. It provides valuable insights into the impact of system improvements related to the introduction of the EAM.