PORTLAND (AP) - Medical malpractice claim payouts in Oregon are lower than those in all but seven other states despite the elimination of a cap on such awards in 1999, a new study shows.

The study researchers tried to measure the effects of various malpractice changes and were surprised how little difference the changes made on the amount and frequency of malpractice awards.

“With some of these types of laws, we were unable to see any effect,” said lead researcher Teresa Waters, an associate professor at the University of Tennessee Health Science Center.

In Oregon the state Supreme Court revoked a cap on damages in 1999 for non-economic losses such as pain and suffering.

Doctors and insurance companies spent $5.2 million in 2004 trying to reinstate a cap, but voters rejected it.

It said some states with caps on damages still had higher-than-average costs from claims while some, including Oregon, retained comparatively low payout rates without caps.

Some states require expert witnesses to practice or to have training in the type of medicine involved. These laws had about three to four times the effect of caps on damage awards, researchers concluded.

Oregon does not have such a program, but eight of the 15 states with the lowest malpractice payments do.

Time limits for suing emerged as the second most influential factor.

Oregon's statute of limitations gives patients two years from the date of discovery of an injury and five years from the date of the treatment.

States with the lowest malpractice awards all had such time limits, researchers found, while the most expensive states either had none or longer ones.

Jim Dorigan, chief executive officer of Northwest Physicians Insurance Co., one of the state's largest malpractice carriers, said the study may have underestimated the cost and frequency of malpractice claims in Oregon.

Dorigan said that in his company's experience, the number of claims per physician is about twice the rate reported in the study, and the average payment was about 50 percent greater for 1999-2003.

Dorigan also questioned the study's findings about the impact of damage caps.

The Oregon Medical Association is backing a bill to require both sides in malpractice cases to disclose who their expert witnesses will be, hoping to encourage earlier settlements and limit frivolous lawsuits.

Malpractice insurance costs are high but are falling for many doctors.

From 2000 to 2004, malpractice insurers raised prices by 30 percent or more a year. But in 2005, Northwest Physicians Insurance lowered average rates for Oregon doctors by 8.3 percent and, in January, the company reduced them by 10 percent.

Dorigan said the number of claims has been falling for reasons that are unclear.

Oregon internists pay $6,000 to $12,000 a year for coverage - less than one-fourth the average price in the five most expensive states. Ob-gyn doctors pay $41,000 to $75,000, or about a third the price in the most expensive states, according Medical Liability Monitor, an industry newsletter.