The evidence in this paper suggests that downgrades by both Moody's and Standard and Poor's are associated with negative abnormal stock returns in the two-day window beginning the day of the press release by the rating agency. Significant negative abnormal performance can still be detected after eliminating observations containing obvious concurrent (potentially contaminating) news releases. There is little evidence of abnormal performance on announcement of an upgrade. Significant abnormal returns are associated with announcements of additions to the Standard and Poor's Credit Watch List, if either a potential downgrade or a potential upgrade is indicated.

This paper documents the effects of large (block) transactions on the prices of common stocks traded on the New York Stock Exchange. We examine whether mean temporary and permanent price effects associated with large and small transactions differ and whether the price effects vary cross-sectionally according to the size of the block. Alternative definitions of block size are investigated – percentage of the equity traded, block volume in relation to normal trading volume, and dollar value of the block. The results suggest that price effects are predominantly temporary for seller-initiated transactions and permanent for buyer-initiated transactions.