Informational efficiency of credit default swap and stock markets: The impact of credit rating announcements

This paper analyzes the response of stock and credit default swap (CDS) markets to rating announcements made by the three major rating agencies during the period 2000–2002. Applying event study methodology, we examine whether and how strongly these markets respond to rating announcements in terms of abnormal returns and adjusted CDS spread changes. First, we find that both markets not only anticipate rating downgrades, but also reviews for downgrade by all three agencies. Second, a combined analysis of different rating events within and across agencies reveals that reviews for downgrade by Standard & Poor’s and Moody’s exhibit the largest impact on both markets. Third, the magnitude of abnormal performance in both markets is influenced by the level of the old rating, previous rating events and, only in the CDS market, by the pre-event average rating level of all agencies.