In principle, credit ratings are based on statistical models of past defaults; in practice, however, with few national defaults having actually occurred, sovereign ratings are often a subjective affair. Analysts at ratings agencies follow developments in the country for which they are responsible and, when necessary, travel there to review the situation.
理论上，评级机构基于过去违约的统计模型；但是，在实践中，国家违约的情况十分罕见，主权评级常常是基于主观做出的。评级机构的分析师追踪他们所负责的国家的发展趋势，必要时到相应的国家去看看情况如何。