Northern Rock and Banking Reform

That is a common misconception about credit rating agencies. The ratings are best viewed on a relative basis: the fact that something is rated AAA does not mean that it is infallible; it means that it is much more credit worthy than something rated AA. If comparators are necessary, a concentration in three or four firms is inevitable, because the agencies require global reach to compare, for example, a small bank in Japan with a large multinational corporation in the United States.