Sovereign Debt Rating Changes and the Stock Market

Using event studies we find statistically and economically significant, negative daily abnormal stock market returns prior to sovereign debt rating downgrade announcements. Instrumental variable techniques show that these findings are more pronounced in countries with lower institutional quality. Our analysis of the frequency and content of news shows that results cannot be explained away by unrelated, concurrent bad news. Instead, we find support for the explanation of leakage, which could take the form of leaked private information to a group of investors, but could also take the form of a rumor that eventually appears in the public domain.