Analysts at Athenahealth looked at provider clients' numbers.

The four big national commercial health insurers take an average of about 23 to 27 days to post payments to providers.

Thirty-five administrators of the traditional Medicare Part B physician services plans take an average of about 21 days to 48 days to pay. Medicaid plan payment speeds range from about 25 days in Connecticut to 107 days in Pennsylvania.

A practice management services firm, Athenahealth Inc. (Nasdaq:ATHN), has included those figures in a new PayerView database. The firm handled about $20 billion in billing for 52,000 U.S. providers in 2013.

See also: 13 Medicare facts you need to know.

Analysts at the firm used information about how public and private payers pay its client providers to rate how the payers perform in many different areas, such as how long they take to pay bills, how likely they are to deny claims, and how accurate they are when they give information about whether they believe a patient is eligible for benefits when the patient is in the office getting care.

The performance spreads for indicators such as claim denial rates seem to be similar to the spreads for payment speed.

In the claim denial rating lists, for example, the big commercial plans look a little worse than the Medicare plans but much better than many of the Medicaid plans. 

Denial rates range from 3.4 percent to 5.4 percent for the big national plans; from 3.4 percent to 8.6 percent for the Medicare Part D plans included; and 5.4 percent to about 38 percent for the Medicaid plans included.