Did Credit Rating Agencies Make Unbiased Assumptions on CDOs?
比较同一评级机构内不同部门对担保债务凭证的假设，发现评级部门的假设比监督部门更乐观，且这些乐观假设的债券更易被降级，表明评级机构存在偏向高评级的动机。
We compare key CDO assumptions from two departments within the same rating agency but with different financial incentives. Assumptions made by the ratings division are more favorable than those by the surveillance department. The differences are not explained by collateral switching during the ramp-up period, a long time gap between reports, nor the collapse of the CDO market in 2007 Additionally, CDOs rated with more favorable assumptions by the ratings group were more likely to be subsequently downgraded. As the useful signals from the surveillance group were seemingly ignored, these findings suggest rating agencies bias towards high ratings.