Do pills poison operating performance?

Contrary to arguments that poison pills degrade firm performance, we find that operating performance modestly improves during the 5-year period after pill adoption. Performance improvements are present in a wide range of firms, and are independent of adoption year and whether the firm is R&D intensive. Although recent arguments suggest that the protection offered by pills is strongest when combined with a staggered board, the performance changes also are unrelated to board structure. This evidence undermines the widely held view that poison pills have systematically negative effects on firm performance.