This meant that the actual risk was ignored since the formula assumed that it could be and had already been calculated using historical and other relevant data and that this knowledge was embedded in the market prices of credit default swaps. The formula was supposed to extract this knowledge from these prices.
For this reason, the use of the formula itself worked to make the actual risk much greater than that calculated by the formula. It led to the absurd lending practices described in the Wikipedia article since their securitization using the formula ignored the very high risk of default on the mortgages originated through these practices.
This ignored risk eventually issued in rates of default, particularly on sub-prime mortgages, much in excess of those anticipated by the formula, the rates described in the Wikipedia article.
Ted