'An obstetrician in Los Angeles, where reforms are in place, pays about $63,000 a year for insurance. That same obstetrician in Miami, with no reforms, pays $277,000 or more.'

"The large jury awards that attract so much public attention actually are rare events and comprise a very small portion of all malpractice payments," said Amitabh Chandra, an economics professor at Dartmouth University, who was the study's lead author. "They're certainly not key drivers of malpractice insurance increases."

Chandra said state regulation of malpractice insurers, as well as the investment practices of insurers themselves, are better explanations for the increase in premiums.

The study covers 184,506 payments that insurers made over a 13-year period ending Dec. 31, 2003. The amount of the payments grew 4 percent annually, which the study described as consistent with the overall increase in health care spending during that time frame.

The average payment grew from $173,018 in 1991 to $263,101 in 2003.

Under federal law, all malpractice payments made on behalf of a licensed health care provider must be reported to the National Practitioner Data Bank within 30 days. The authors relied on the data bank for their study.

'They Go Where the Business Is'

While the authors dismiss the importance of the caps in curbing premium increases, doctors certainly have not dismissed their importance, according to a separate study published in the same issue.

The authors studied the growth in the number of physicians per 100,000 residents from 1970 to 2000. The authors found that the number of doctors increased 83 percent in states that had no cap on noneconomic damages. The growth rate was slightly higher, 86 percent, for states enacting caps in the 1970s. The growth rate was much higher, 102 percent, for states enacting caps in the 1980s.

The researchers said they factored in various items that might account for the increase in physicians, such as income and unemployment rate, death rates for a variety of diseases, racial composition of the community and whether a medical school was in the area.

Frank Clemente, a spokesman for the consumer advocacy group Public Citizen, said many of the states that have enacted caps are conservative states in the South, where there has been large population growth. "Doctors are like anybody else, they go where the business is," he said.

Patient Access to Care

President Bush supports a proposal that caps payments for pain and suffering at $250,000 in medical malpractice cases. Congress has so far not passed such legislation.

The American Medical Association, the lobbying group for doctors, said the study showed that caps on noneconomic damages work to ensure patient access to care.

"An obstetrician in Los Angeles, where reforms are in place, pays about $63,000 a year for insurance," said Donald Palmisano, immediate past president of the American Medical Association. "That same obstetrician in Miami, with no reforms, pays $277,000 or more."