Despite this, Quality Planning said some auto insurance companies are eliminating annual mileage as a rating factor.

Bob U'Ren, senior vice president at Quality Planning, said data verifying the decrease in use of annual mileage as a rating factor was provided by insurers that work with Quality Planning, and includes both large and small companies.

Additionally, many insurers have broad mileage bands that prevent them from offering competitive pricing based on mileage, Quality Planning said.

The study noted that within broad mileage ranges, for example, zero to 7,500 miles, loss costs can be 12 to 15 percent higher for drivers at the high end of the mileage band, and 20 to 25 percent lower for drivers at the low end of the mileage band, as compared to the average for that range.

"Consumers justifiably believe that if they're driving less, they should pay less for their insurance, and indeed the claims statistics support that," said Dr. Raj Bhat, president of Quality Planning. "Our study shows that those insurers who fine-tune their premium to a customer's driving habits will be better positioned to offer competitive pricing."

Robert Passmore, director of personal lines for the Property Casualty Insurers Association of America (PCI), said mileage is an important factor, but he pointed to problems insurers have with verifying miles driven.

Insurance products based on a "Pay As You Drive" concept, for example, in which rates are based on miles driven, sometimes use GPS devices to monitor miles driven, but Mr. Passmore noted that these devices have raised privacy concerns in some states.

He said consumers should know up front what such devices track, how that information is used, and how the information is protected from misuse.

Tim Cox, spokesman for Quality Planning, said there are other ways to track mileage besides GPS devices. Quality Planning, for example, uses methods such as car service databases to compile information, he said.

When a car is serviced or is taken for an oil change, the auto shop may record the mileage. Companies can harvest information from those databases to determine mileage readings, Mr. Cox said.

Mr. Passmore said as tools are developed that provide insurers with accurate information, and if those tools are approved for use, then insurers can use mileage as a rating factor in a more refined way.

For the survey, Quality Planning sampled 459,599 single-vehicle policies from multiple carriers during 2003 to 2006. The claim data from that period, the company said, was used to evaluate policy period claim costs. The annual mileage estimates were obtained from Quality Planning's RISK:check process, which the company said uses statistical estimates and odometer readings, when available.