By Hal M. Bundrick

NEW YORK (

MainStreet

) -- If you don't have a college degree and you struggle to makes ends meet in a blue-collar job, chances are good that you're paying more for

car insurance

, according to the Consumer Federation of America (CFA). For example, buying the minimum liability coverage required, the CFA says that GEICO often charges a factory worker with a high school degree far higher annual premiums than

a plant supervisor with a college degree

--in fact 45% more in Seattle ($870 vs. $599), 40% more in Hartford ($1,299 vs. $926), 33% more in Oakland ($922 vs. $693), 23% more in Louisville ($2,200 vs. $1,791), 21% more in Chicago ($1,013 vs. $840), and 20% more in Baltimore ($1,971 vs. $1,647).

Read: 5 Must-Have Disaster Apps

The study also says these differences would be even greater if, for education, the comparisons also included no high school degree and a graduate degree. For example, the Baltimore factory worker would pay an annual premium of $2,061 with no high school degree, an annual premium of $1,971 with a high school degree, an annual premium of $1,801 with a college degree, and an annual premium of $1,722 with a graduate degree.

But other major insurers bust the chops of working folk, too. Progressive also often charges a factory worker with a high school degree higher annual premiums than a plant supervisor with a college degree - 33% more in Baltimore ($1,818 vs. $1,362), 14% more in Houston ($1,406 vs. $1,236), 9% more in Louisville ($2,390 vs $2,185), 9% more in Denver ($995 vs. $911), and 8% more in Oakland ($736 vs. $684).

This trend is wide-spread. Liberty Mutual, for example, charges a high school graduate higher annual premiums than a college graduate - 13% more in Baltimore ($2,116 vs. $1,877), 13% more in Houston ($1,373 vs. $1,216), 12% more in Phoenix ($1,592 vs. $1,418), and 10% more in Hartford ($1,913 vs. $1,735). In five other cities studied - Atlanta, Louisville, Chicago, Denver, and Seattle - Liberty's website quoted rates for a college graduate but not for a high school graduate.

Read: Oklahoma Relief Efforts Feature Small Businesses and Local Heroesl

In many cities, Farmers Insurance charges those who are neither professionals nor certain government workers 5% higher premiums.

For each of these comparisons, all other factors, including a perfect driving record, were held constant.

"Auto insurers charge high premiums for minimal coverage to most working people even those with perfect driving records, who live in urban areas," said Stephen Brobeck, CFA's Executive Director. "Since most Americans need a car and almost all states require the purchase of auto insurance, many lower-income workers are faced with the choice of paying these high, and often unaffordable prices, or breaking the law by driving without insurance," he added.

CFA estimates that one-quarter to one-third of drivers with household incomes under $36,000 - accounting for 40% of all households - are uninsured.

The consumer group says that while many states prohibit the use of education and occupation to deny coverage, they do permit the use of these factors in setting rates. That may help explain why some quoted annual premiums for minimum liability coverage are so high - sometimes exceeding $3,000, even $4,000. CFA claims that these high rates, which few drivers if any pay, effectively deny low- and moderate-income consumers coverage.

Read: Avoid Popular Stocks like the Devil

"Since state governments require purchase of auto insurance, state insurance commissioners have an obligation to address this issue," Broebeck says. "And the relatively new Federal Insurance Office should make the study of this problem a priority."

State Farm, Allstate, USAA, Nationwide and Travelers apparently do not use education or occupation in their rate-making, at least in the ten states examined by CFA.

--Written by Hal M. Bundrick for MainStreet