In this study, we investigate why the Big Three rating agencies, namely, Standard and Poor’s, Moody’s, and Fitch, may simultaneously assign (in)accurate ratings. We propose safety and revenue concerns as motivations to their herding behavior and empirically test them thereafter. Safety concern motivates agencies to follow the ratings of other agencies to ensure safety in a sense that if all agencies make the same errors, then no one will be blamed. Revenue concern motivates agencies to upgrade their ratings to attract customers when their ratings are lower than those of their rivals. Our results first show that safety concern is the major driver for the herding behavior. Second, motivation undergoes structural changes from a revenue concern in the pre-crisis period to safety concern during the crisis and post-crisis periods. Third, results support the safety concern even when an agency and their rival’s ratings move between investment and speculative grades.

在这项研究中，我们调查了为什么三大评级机构，即标准普尔、穆迪和惠誉，可能会同时分配（不）准确的评级。我们建议将安全和收入问题作为其放牧行为的动机，然后对其进行实证测试。安全关注促使机构遵循其他机构的评级以确保安全，如果所有机构都犯同样的错误，那么没有人会受到指责。当评级低于竞争对手时，收入问题会促使代理商提高评级以吸引客户。我们的结果首先表明安全问题是放牧行为的主要驱动因素。其次，动机经历了结构性变化，从危机前的收入问题到危机和危机后时期的安全问题。第三，