As Japan gives more say to investors, companies are clinging to a tool that has the opposite effect.

Poison pills, a way to scupper hostile takeovers, are in place for at least 20 percent of firms in the benchmark Topix index. That compares with at least 5.8 percent for Wall Street¡¯s Standard & Poor¡¯s 500 Index.

Prime Minister Shinzo Abe is seeking to instill more market discipline on Japan¡¯s companies by making management more accountable to investors. The lingering prevalence of defense measures suggests a reluctance in the nation¡¯s boardrooms to buy into the premier¡¯s plans. For Institutional Shareholder Services Inc., the pills are also unnecessary.