We study the relationship of corporate governance policy and idiosyncratic risk. Firms with fewer antitakeover provisions display higher levels of idiosyncratic risk, trading activity, private information flow, and information about future earnings in stock prices. Trading interest by institutions, especially those active in merger arbitrage, strengthens the relationship of governance to idiosyncratic risk. Our results indicate that openness to the market for corporate control leads to more informative stock prices by encouraging collection of and trading on private information. Consistent with an information‐flow interpretation, the component of volatility unrelated to governance is associated with the efficiency of corporate investment.

The evidence here indicates that sovereign debt rating and credit outlook changes of one country have an asymmetric and economically significant effect on the stock market returns of other countries over 1989–2003. There is a negative reaction of 51 basis points (two-day return spread vis-á-vis the US) to a credit ratings downgrade of one notch in a common information spillover around the world. Upgrades, however, have no significant impact on return spreads of countries abroad. Closeness (e.g., geographic proximity) and emerging market status amplify the effect of a spillover. Downgrade spillover effects at the industry level are more pronounced in traded goods and small industries.