athenahealth (NASDAQ:ATHN) is out with its annual review of how quickly health insurers are paying the claims that doctors make for services. Based on 41 million medical charges, athenahealth said that the national health insurers were taking about a month to pay their bills.

Company

Days in Accounts Receivable

Humana (NYSE:HUM)

26.7

Aetna (NYSE:AET)

28.4

Cigna (NYSE:CI)

30.0

UnitedHealth Group (NYSE:UNH)

33.2

WellPoint (NYSE:WLP)

35.9

Coventry Health Care (NYSE:CVH)

38.5

Source: athenahealth.

It seems to me that investors shouldn't be too upset about where the companies they invest in fall on the list. After all, that's partially how insurance companies make money: by collecting interest on investments they make between when they collect the premium and when the claim is paid out. For them, the longer it takes to pay, the better.

Of course, the companies have to keep it within reason. Doctors and hospitals are willing to put up with delayed payments, but only to a certain degree. If an insurer stretched out payments far enough, doctors might be inclined to drop patients who use that insurance. The U.S. government's Medicare part B is paying charges in 33.4 days, so it seems that all these insurers are still in the reasonable range and probably aren't in danger of getting dropped.

athenahealth also tracks other items, like denial rate, which might affect how patients feel about their insurers, but I'm not sure how much that matters. Many people only have one choice from their employer, and those who do have multiple choices often pick based on price and coverage. The service provided by the insurer is often a distant third.

Health insurers are in an interesting industry where the end users -- doctors and patients -- often don't make the decision about which company to use. That makes any list that isn't based on price fairly meaningless.

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Coventry Health Care and UnitedHealth are Motley Fool Stock Advisor picks. UnitedHealth and WellPoint are Motley Fool Inside Value recommendations. Try any of our Foolish newsletters today, free for 30 days.

Fool contributor Brian Orelli, Ph.D., doesn't own shares of any company mentioned in this article. The Fool owns shares of UnitedHealth and has a disclosure policy.