Credit rating agencies (CRAs) are expected to provide investors with an informed and unbiased view on securities' debt risk; the risk that issuers will fail to make promised interest or principal payments when they are due. The agencies provide judgements on the creditworthiness of bonds issued by a wide spectrum of entities, including corporations, non-profit firms, special purpose entities, sovereign nations and state and municipal governments. This book explores the regulation and reform of credit rating agencies with a focus on their performance and failures in recent years.