Credit ratings of corporations are biased, but the forces driving this bias are unclear. We argue it would be difficult for rating agencies to issue high grades for a firm’s debt when there are a lot of objective equity analyst reports about the firm’s earnings that are informative about its default. We find that an exogenous drop in analyst coverage leads to greater optimism-bias in ratings, especially for firms with little bond analyst coverage and those that are close to default. This coverage-induced shock leads to less informative ratings about future defaults and downgrades and more subsequent bond security mispricings.