Insurers use multiple criteria to set auto rates, including a driver’s age, driving record and typical annual mileage. Criteria vary, since state governments set insurance rules. Some states allow consideration of a person’s credit history — the better your credit score, the more you save — so it helps if you pay your bills on time. Some let insurers consider a customer’s marital status and occupation. At least a half-dozen states, including California, have banned the use of a driver’s sex in setting insurance rates. (Nationally, women pay rates that are about 1 percent higher, The Zebra found, but the disparity is greater in some states.)

Other criteria are based on the vehicle, such as the model year and whether it’s a sedan or a truck.

One way to keep premiums down, say industry experts and consumer advocacy groups, is to compare quotes from different insurers, ideally every year or two.

“It’s worth a little bit of effort,” said J. Robert Hunter, an insurance expert with the Consumer Federation.

If you find a lower rate, state insurance department websites often offer information about consumer complaints, to help you evaluate a company’s record of handling claims before you switch. You may want to go beyond the most visible brands: Consumer Reports recently included some lesser-known companies, like the Rhode Island-based Amica Mutual Insurance, among its highly rated insurers.

Another way to lower your premium is to increase your policy’s deductible, the amount of money that you must pay before insurance coverage begins. (With a $500 deductible, you would pay $500 for a $1,000 claim.) Raising your deductible to $1,000 from $500 will save an average of 13 percent on your premium, The Zebra found. Just be sure to put money aside so you can afford to pay the deductible if you have a claim, said Jon Linkov, the deputy auto editor at Consumer Reports.

And be careful not to let your policy lapse, said Nicole Beck, a spokeswoman for The Zebra. Even a short gap, she said, could trigger a substantial increase when you buy a new policy.