Bond review and rating change announcements: An examination of informational value and market efficiency

This paper examines the impact of announcements of both bond rating reviews and rating changes on equity returns. We find that announcements of review for possible down grading of debt have a significant negative effect on stock prices while subsequent actual downgrades have a negligible impact. Further, we find that press releases convey new information to the market whereas the subsequent reporting of this information in the financial press causes little market reaction. We conclude that extreme care regarding details of the dissemination of financial information must be exercised in any event study.