External ratings represent an independent opinion of credit experts that evaluate the overall creditworthiness of an issuer and its issues. Running from AAA to D, they serve as an indicator for the increasing probability of default, i.e. risk. During recent credit market turmoil many investors lost a fortune due to unforeseen defaults of issuers and a downslide of yields. In the following, internationally renowned rating agencies were blamed for having failed in fulfilling their gatekeeping role. By describing the rating process and the underlying rating criteria, the author reveals the deficiencies of external ratings. Understanding the interdependency of ratings and market expectations, the reader gains insight into what has happened before and during the financial crisis. Finally, the author provides an outlook on changes in and challenges of a recovering rating industry. This book is addressed to those who feel unsecure about the expressiveness and credibility of ratings. Questioning the informative value of ratings and clearly showing the limits, it gives valuable advice on how to consciously operate with ratings.