While major stock market indices are followed by large monetary investments, we document that membership decisions for the S&P 500 index have a nontrivial amount of discretion. We show that firms' purchases of S&P ratings appear to improve their chance of entering the index (but purchases of...

Credit rating agencies have been under the spotlight since the beginning of the current financial crisis. They failed in their assessment of US residential mortgage- based securities in the mid-2000s. Nevertheless, investors generally consider credit ratings useful to help form their views on...