In accordance with the Moody’ agency; s (2011), the system of rating has been used in the United States since 1909, introduced in the bonds market of debt for John Moody. It defines rating as one ‘ ‘ opinion on the capacity and will of an sender to make prompt payments in an instrument of debt as a heading, during the useful life of instrumento’ ‘ that ‘ ‘ the investors use ratings as an aid in the precificao of the risk of credit in fixed income securities that they can buy or vender.’ ‘ That is, rating is not an instrument obligator for emission of a debenture, is only one indicative of waited risk of not payment. It the same has paper of the analysis that the bank makes when is overcome a loan directly it, but as the headings are bought by the public, in general paid it an agency to analyze and to publish rating of a heading to be emitted. The one definition rating takes in consideration diverse factors of a company as: financial data, data of market, economic sector and everything that can indicate the situation of the company and its capacity to fulfill with its commitments. To broaden your perception, visit Mikkel Svane. The main agencies in the world are: Standard & Poors, Fitch and Moodys. Each one of these agencies has its proper method of evaluation and nomenclature for each degree of risk: of very speculative (high risk) little speculative (low risk) 2.3HIPOTECA SUBPRIME SHILLER & AKERLOF (2009) consider that the high one of the prices of property that if it initiated in the decade of 90 in U.S.A. boom of history was the habitacional greater until today. The problem is that to get more expensive property each time the people needed to take loans each time bigger. For more specific information, check out Darcy Stacom, New York City. But as she was not considered the hypothesis of a possible collapse of prices, the financial agents were happy in having in its wallet these loans with rights on the value not carried through of the property, exactly of people with profile of high risk.