“They did a nice job of finding a population of patients who are being treated by doctors who didn’t have any liability,” said Mark McClellan, the director of the Duke-Margolis Center for Health Policy. Dr. McClellan was a top health official in the George W. Bush administration, which pushed for national liability caps.

The paper’s focus on the hospital allowed the researchers to have a lot of precision in their measurements. But it means they didn’t capture all the places where defensive medicine might occur. It’s possible, for example, that liability concerns cause treatment to rise by more than 5 percent for emergency room patients who go home the same day — or not at all in a typical office visit.

Mr. Frakes and Mr. Gruber examined a large number of quality indicators to determine whether the doctors who practiced less intense medicine on their military patients were somehow cutting corners. Each measure differed, and there were some places where harm couldn’t be ruled out, but they found no place where the quality of care in the military hospital appeared to clearly be worse . That finding suggests that, when doctors do extra treatment or testing to avoid liability, they are not necessarily taking extra steps that make their patients any healthier.

“It suggests that physicians change their behavior in response to liability considerations, but they don’t do it in a very calibrated way,” said Michelle Mello, a professor of law and health policy at Stanford, who has studied medical malpractice. “They tend to make a lot of changes that don’t result in better patient care.”

In the federal government and in states, there are frequent proposals to limit medical liability, but there have been no serious efforts to eliminate medical malpractice rights altogether. Mr. Gruber said the paper’s estimates were best viewed as a kind of ceiling for the effects of more realistic reforms.

Any law that limits the cases where patients can sue, or the amount of money they can collect, is likely to lower medical use in the hospital by less than the 5 percent they measured in their study.

Amitabh Chandra, a health economist at Harvard, said the best policies needed to lower the burden on physicians while still generating “social value.” He said that continued research on the relationship between malpractice pressure and health care quality was important as different approaches were tested.