Corporate Governance, Shareholder Rights, and Shareholder Rights Plans: Poison, Placebo, or Prescription?
研究毒丸计划对公司价值的影响，发现只有在治理结构最民主（保护性条款最少）的公司中，毒丸计划才带来显著的正向股票收益和盈利增长预测上调。
Abstract We examine the effect of poison pill adoptions on firm value, controlling for the adopting firm's preexisting corporate governance structure. We find that only companies with the most democratic governance structures, defined as those with the fewest preexisting protective governance provisions, experience significantly positive abnormal stock returns and significantly positive abnormal revisions in five-year earnings growth rate forecasts. Moreover, regression results indicate that abnormal returns and forecast revisions are significantly related to governance structure and not to board composition or subsequent merger activity.