The American Medical Association has released its second National Health Insurer Report Card, which measures the nation's eight largest health insurers on claim denials, timeliness, accuracy, and transparency. According to the report, the percentage of medical claims denied in 2008 ranged from Medicare's 6.9% to UnitedHealthcare's 2.7%. The percentages improved this year, ranging from Anthem Blue Cross Blue Shield's high of 4.3% to Aetna's low claim denial rate of 1.8%.