Your calculation shows why the crisis happened

U think you can 得到结果的几率, the rating agents were doing exactly the same with all the historical data. And the relationship changed under subprime and other pressures, you got what you deserved (Garbage out).
I believe the Behavioral economics. If you want to study the stock market, you need study it like history. First it is always how the human interaction happen. It is not 布朗运动.