When credit scores are used to determine automobile insurance rates, a typical 30-year-old single woman living in a major city with a good driving record and an annual income of about $30,000 would pay as little as $563 or as much as $1,277 in insurance premiums, according to research by the Consumer Federation of America.

Exactly what she ends up paying would depend on whether her credit score was poor or excellent, and the consumer advocacy group questions whether that’s fair.

“Americans reject auto insurers’ use of credit scores because they don’t think someone who’s had difficulty paying debts should automatically be charged higher auto insurance premiums,” said Stephen Brobeck, executive director of the Washington, D.C.-based organization.

“After all, if drivers don’t pay their insurance premiums, insurers are not obligated to pay claims,” he said.

In the past, the only things that mattered when it came to setting auto insurance rates were the driver’s age, gender, driving record and type of car.

But credit scores have begun to play a role in what rates insurance companies charge. The Consumer Federation studied data from the two largest auto insurers – State Farm and Allstate – to see how low-income drivers are hurt by the practice.

Only three states – California, Massachusetts and Hawaii – have prohibited insurer use of credit scores in setting auto and home insurance prices.

The Insurance Information Institute, a New York-based trade association, argues that there is a strong correlation between credit scores and insurance claims, noting that drivers with the lowest credit scores file 40 percent more claims than drivers with the highest credit scores.

“There is a very significant difference in the loss performance of individuals with high credit-based insurance scores relative to individuals with poor scores,” said Bob Hartwig, president of the Insurance Information Institute.

Credit reporting agency FICO estimates that, where permitted, 95 percent of auto insurers use credit scores in their pricing of insurance policies.

Because auto insurer websites do not permit consumers to input credit scores, it was difficult for Consumer Federation researchers to examine the data. So researchers purchased price information related to credit scores for State Farm and Allstate from Quadrant Information Services, an independent data services company that aggregates insurance premiums.

The Consumer Federation found a strong correlation between credit scores and annual auto insurance premiums.

Prices charged by State Farm were at least 94 percent higher for “poor” than for “excellent” credit scores, with an average of 127 percent higher. In the Baltimore test market, prices ranged from $2,788 for a poor score to $1,030 for an excellent score for State Farm Mutual.

Allstate prices tended to be higher than State Farm prices, but the range was not as extreme for poor and excellent credit scores. The Consumer Federation did not specify what an excellent or bad credit score was, nor the range for an excellent or poor score.