The influence of standard and poor's ranking changes on stock price performance

Describes Standard and Poor's (S&P: USA) star ranking system for firm performance and presents a study of the impact of ranking changes on share prices. Outlines previous research on the effect of ranking changes and examines the share prices for 70 days before and after S&P ranking change announcements 1993-1995 to assess abnormal returns. Explains the methodology and presents the results, which show significant changes in abnormal returns around the announcement dates, especially where the change is "in leaps rather than in steps".