Rebecca Prather says she owns her Fairfax County home, has no mortgage and pays off credit card accounts monthly. So she was "shocked" recently when Allstate offered her a homeowner's insurance policy at its second-best rating.

She knows insurance companies use credit histories and credit scores to underwrite policies and set premiums, so she couldn't believe that her "squeaky clean credit," plus having no past insurance claims, didn't equal Allstate's best rate.

Turns out that "Allstate won't give me their best credit rating because I have had a number of credit cards for short periods rather than a few for a long period," says Prather, who likes to sign up for new credit-card promotions that offer low interest rates or rebates.

This raises concerns to credit raters. "If you have a lot of credit cards, that can be something bad because you are trying to run up debt," she says. "Or, it can be good, as in my case, because I'm trying to take advantage of these offers to do a better job of managing my money. They don't make that distinction."

Credit-based insurance scores are confidential numerical rankings similar to the credit scores that major credit bureaus calculate using about 30 factors from a consumer's credit history and current accounts. The credit score reflects a consumer's credit-worthiness. Insurance companies use their own formula to predict insurance claims risks.

"Actuarial studies show that how a person manages his or her financial affairs, which is what an insurance score indicates, is a good predictor of insurance claims," according to the Insurance Information Institute, the D.C.-based industry group. "Statistically, people who have a poor insurance score are more likely to file a claim."

But insurance scoring has been controversial. While insurers say two-thirds of policyholders have a lower premium because of good credit, many consumers and lawmakers are wary. Forty-eight states -- including Maryland and Virginia -- have taken actions that restrict credit scoring in insurance underwriting, such as prohibiting insurance companies from denying coverage or canceling policies based solely on credit information, and requiring insurers to disclose primary factors on which any adverse action is based. The Federal Trade Commission is studying the impact of credit scores and credit-based insurance scores on price and availability of policies.

For Prather, the difference between the best and second-best premium isn't that much -- $368 a year instead of $352. But the retired computer specialist considers it a $16 penalty for being a smart consumer.

But what bothers her more is that Allstate won't give her a straight answer about what she can do to get its best deal, she says. "They won't tell me how close my score is to their cutoff for the next higher or lower rating, or how a new credit card would affect it."

Allstate says its insurance scoring method is "proprietary information" that involves too many factors to translate into a simple answer, but Prather can request that her credit score be reviewed at any time, and the new score will then change her premium -- for better or worse.

"I can't get enough specifics from them to enable me to make an intelligent decision on this matter," complains Prather.

Allstate Insurance spokesman Bill Mellander says the company's confidentiality policy prevents him from addressing Prather's specific policy or problem. "Generally speaking, simply opening a credit card account, even to take advantage of special offers, does not mean a consumer will have a poor insurance score . . . and does not mean you will not receive the lowest rate offered by a particular insurer," he says.

Maxine Sweet, vice president of consumer education at Experian, one of the national credit reporting bureaus, agrees that insurance companies can't distinguish how much a single factor weighs in calculating a score. "No one can tell how changing one item on a credit report will precisely affect a score," says Sweet. "It is impossible to direct someone to change one item and expect the score to increase by a known amount."

Mellander recommends that a consumer who is asking questions about how much this or that is going to affect a credit score should "contact a professional or a financial adviser who can give them some honest, solid advice."

Prather would like to see tougher laws requiring insurance companies to disclose information that helps consumers make smart choices. "As long as companies like Allstate keep their calculations secret," she says, "no other party can help a person like me make an informed decision because we can't get the necessary info."

Got questions? A consumer complaint? A helpful tip? E-mail details to or write Don Oldenburg, The Washington Post, 1150 15th St. NW, Washington, D.C. 20071.