After reviewing 275 quotes for basic liability coverage from five large insurers, the CFA said that it found:

- Consumers saved only $30 per year, or 1.6 percent, on average for every 5,000 fewer miles driven annually, excluding California drivers, who saved $81 on average, or 8.7 percent.

- Outside of California, premiums for very low-mileage drivers (2,500 miles/year) were only $102 lower, on average, than very high-mileage drivers (22,500 miles/year), a savings of about six percent annually. (This excluded Allstate in Tampa, where a minimum coverage quote was not provided.)

- In Los Angeles, very low-mileage drivers saved $346, or 30 percent, compared to very high-mileage drivers.

- Outside of California, Farmers and Progressive provided no mileage-based savings in tested cities, GEICO offered a small price reduction, while Allstate's and State Farm's lowest-mileage customers saw average savings of 11 percent and 13 percent, respectively, compared with the highest-mileage drivers.

"How well you drive and how much you drive should be the primary factors considered when insurance companies set premiums, but we have found that many companies either entirely ignore their customers' actual mileage or give such a pittance for low mileage as to have no meaningful impact on rates," said J. Robert Hunter, the CFA's director of insurance and former insurance commissioner of Texas. "For people in most parts of the country, with California as the notable exception, you'll often pay about the same auto insurance premium whether you commute 90 miles round trip every day or if you take public transit to work and only drive on the weekends. If you drive less, you should pay less, because you can't crash when you're not driving."

When insurance companies diminished the impact of mileage in their pricing methods, lower-mileage drivers were punished for reducing their risk by having to overpay for coverage, according to the CFA.

For its research, the CFA sought online premium quotes for basic liability coverage from Allstate, Farmers, GEICO, Progressive, and State Farm for a driver with an unblemished record in which the only difference in each quote was the number of miles driven; CFA sought five different quotes in 5,000-mile increments between 2,500 and 22,500 miles annually per company in each of the 12 cities tested. The cities tested were Atlanta, Baltimore, Boston, Charlotte, Chicago, Cleveland, Houston, Los Angeles, Minneapolis, Oklahoma City, Rochester (New York), and Tampa. 

Among the 12 cities tested by CFA, only drivers in Los Angeles saw consistent savings for lower mileage driving, with premiums dropping by an average of 8.7 percent for every reduction of 5,000 miles per year and very low-mileage drivers paying 30 percent less than very high-mileage drivers. Under California law, auto insurers are required to give drivers' annual mileage the second most weight when determining their premiums, with driving record being given the most weight.

Drivers in other cities saw average savings of only about 1.6 percent for every 5,000-mile annual reduction, which, according to the CFA, amounted to less than $3 savings per month:

- Motorists in Charlotte, Minneapolis, Houston, Oklahoma City, Rochester, and Cleveland saw 1.5 percent or lower savings for mileage reduction;

- Chicago and Baltimore drivers received less than two percent savings; and

- Drivers in Boston, Atlanta, and Tampa earned less than three percent for scaling back their mileage.

Even huge drops in annual mileage yielded only minor premium savings in most parts of the country, according to the CFA. The CFA said that it compared motorists who drove 2,500 miles per year with those who drove 22,500 miles per year and found limited benefits to most drivers tested. Only about a quarter of drivers outside of California would receive a 10 percent cut and in only one of 50 tests outside of California did a driver receive 20 percent savings or more for driving 20,000 miles less than another driver. Savings for the very low-mileage drivers were over 28 percent from four of five companies in California.

Although all five companies provided discounts for lower mileage driving in California, the companies' track record in other states was "much worse," the CFA said, as shown below:

According to the CFA, that insurers did not give much benefit to drivers for reducing risk by reducing the miles they drive contrasted with company website statements that explained why lower-mileage drivers should see savings. For example:
- State Farm: "The more miles you drive in a year, the higher the chances of a crash – regardless of how safe a driver you are…. Consider joining a car or van pool, riding your bike, or taking public transportation to work. If you reduce your total annual driving mileage enough, you may lower your premiums."

- Allstate: "Insurers typically look at how much you use your car. Someone who has a long commute to work may pay more for insurance than someone who only uses their vehicle to run errands on weekends – since more miles behind the wheel mean more exposure to risk."

- GEICO: "How much you drive each year can increase your auto insurance rates because it places you more at risk of being involved in an accident. People who drive fewer miles than average are usually eligible for lower rates on their auto insurance."

- Farmers: "Driving less could save you a bundle not only on gas but also on your premium. If it's an option, try moving closer to work or carpooling. Infrequent drivers are at a lower risk of being involved in an accident, and may therefore enjoy low-mileage discounts."

- Progressive, singularly, acknowledged that it did not differentiate between low- and high-mileage drivers ("In the large majority of states, we won't even ask about your mileage. You'll pay the same rate whether you drive 50 or 5,000 miles a week!"). Instead, Progressive solicited customers to sign up for its driving monitoring program that, the company claimed, measures drivers' hard braking, late night driving, and miles driven. The company provided a zero percent to 15 percent discount to participants in the program.

"The insurance industry knows that how many miles people drive each year is directly related to their risk of being in an accident, but companies consistently ignore this and charge drivers higher rates even when they are lower risks," said Douglas Heller, who conducted the analysis with CFA researcher Michelle Styczynski. "At the same time, many of these companies feel perfectly at ease charging lower-income drivers with perfect records higher rates than well-to-do customers based on factors like their job title, education level, credit score, and whether they rent or own their home."

The CFA called on state lawmakers and insurance commissioners to demand that auto insurance rates be more closely tied to drivers' mileage.

"Precisely how much premiums should fall when a driver decides to carpool to work instead of always driving themselves is a reasonable actuarial exercise but charging the same amount to a 5,000-mile driver and a 20,000-mile driver is undeniably unfair," said CFA's Hunter. "Since insurers won't give low-risk drivers a break, consumer protection rules should require it." 

David Snyder, the vice president of policy, research, and international matters for the Property Casualty Insurers Association of America ("PCI"), said in response to the CFA study:

This is the latest in a long series of studies from the Consumer Federation of America based on flawed research and a fundamental misunderstanding of auto insurance underwriting and rating.

Insurers use a wide variety of factors that have proven to be effective in predicting the likelihood of someone filing an insurance claim, how costly that claim may be, or having a loss. By using a variety of rating factors, insurers are able to develop a more complete picture of a driver's potential for filing a claim and in this way more accurately price the policy.

The report itself demonstrates that mileage is often considered but, as one would expect in a competitive market, it is done so differently among insurers. Additionally, there are issues of validation and just using minimum coverage as the report does may not reflect the full range of differences of rates including mileage. In addition, it appears to ignore discount plans offered by some of the carriers, such as usage-based insurance programs, which monitor the way someone drives, where they drive and how often they drive. Those programs and other rate filings have documented that while vehicle mileage is relevant, how you drive and the conditions you drive under, such as congestion, are more important in predicting risk of loss.

However, predicting future losses has actually gotten more accurate as a result of insurers' use of additional data and factors. Consumers should be assured that auto insurance pricing is closely scrutinized by state insurance regulators and it is subject to rigorous actuarial standards which ensures that rating factors accurately measure risk and comply with the law.

What the study does reinforce is that consumers should seek quotes from several auto insurers since the auto insurance market is highly competitive, and consumers have a large variety of choices.