Deviations from put-call parity contain information about future stock returns. Using the difference in implied volatility between pairs of call and put options to measure these deviations, we find that stocks with relatively expensive calls outperform stocks with relatively expensive puts by 50 basis points per week. We find both positive abnormal performance in stocks with relatively expensive calls and negative abnormal performance in stocks with relatively expensive puts, which cannot be explained by short sale constraints. Rebate rates from the stock lending market directly confirm that our findings are not driven by stocks that are hard to borrow. The degree of predictability is larger when option liquidity is high and stock liquidity low, while there is little predictability when the opposite is true. Controlling for size, option prices are more likely to deviate from strict put-call parity when underlying stocks face more information risk. The degree of predictability decreases over the sample period. Our results are consistent with mispricing during the earlier years of the study, with a gradual reduction of the mispricing over time.

Poison pills are among the most powerful antitakeover provisions, but studying their economic impact is challenging because of the obvious endogeneity concerns. We address the problem by studying U.S. states’ staggered adoption of poison pill laws (PPLs), which strengthen the right to adopt a pill (i.e., the shadow pill ) and increase the validity of visible pills. We document that PPLs make visible pill policy aligned with economic incentives, increasing pill adoption among firms with a high likelihood of takeover, but decreasing it among firms with low takeover likelihood. We also document that PPLs positively impact firm value, especially for innovative firms with more intangible assets.