The information is not readily available - it is proprietary to the insurance companies, and it. Also, it varies state-by-state. Some states, for instance, allow the person's credit score to be a reason to deny insurance, others don't allow denial based on credit scores, and others don't allow credit scores to be considered at all.
Since auto insurance did not exist in 1789, when the Constitution came into being, regulation of it falls to each State, as the Federal government cannot regulate anything it is not authorized to regulate in the constitution. Each auto insurance company hires teams of statisticians to try to find predictors of those who will file claims. Safe driving history is, of course, part of that. But companies found that people with poor credit scores tended to make more claims, so they tried to use that, as well. Competing against one another, they will try anything to get ahead of their competitors and make more money. State regulations can't keep up. And they don't have to say how they create their rates. Occasionally, articles are published about how rates are being determined, but I'm not aware of any regular publication of criteria.