The percentage of physicians who provide free care to the poor has dropped over the past decade, signaling a growing problem for the uninsured, a survey suggests.

About three-quarters of physicians provided charity care in the mid-1990s, compared with about two-thirds now, according to a study being released Thursday by the Center for Studying Health System Change.

The numbers have declined across all major specialties. The highest rate of free care, 78.8 percent, comes from surgeons, perhaps because many of these doctors treat uninsured patients in emergency rooms.

Just over 60 percent of pediatricians provided free care, the lowest rate among the specialties. That could be because children are more likely than adults to have insurance coverage.

Dr. Peter Cunningham, senior researcher for the center, said he believes the drop in charity care reflects two trends:

--stagnant reimbursement rates from the government and lower fees that insurers are negotiating on behalf of their customers.

"In the past, a lot of physicians were able to afford it because they could charge paying patients higher rates," Cunningham said.

--more physicians are leaving solo practices to join large group practices.

"This means they have less control over the types of patients they see," Cunningham said.

The president of the American Medical Association said he was not surprised by the findings. Dr. J. Edward Hill, a family physician from Mississippi, said doctors are committed to providing charity care, but many are constrained by time and finances.

He noted that the average doctor completing residency has about $119,000 in debt.

"Charity care is not the solution to our health coverage problems in this country," Hill said. "Maybe this will help wake up everybody so they understand we've got to solve the problem of almost 46 million people without (insurance) coverage."

Hill said the AMA supports the use of tax credits to make health insurance more affordable and changes in insurance regulation that would reduce costs.

The study said 81 percent of doctors with their own practice or with a two-person office provide some charity care.

The percentage of doctors providing charity care drops to 66 percent when they practice with 11 to 50 other physicians. It drops even further, to 62 percent, when physicians practice in a group of more than 50 physicians.

"With fewer physicians providing charity care, it's going to drive more uninsured people to seek care in hospitals emergency rooms," Cunningham said. "Care in emergency rooms is more costly, it's less efficient."

The center, a nonpartisan group that conducts health research, took its telephone survey of about 6,600 physicians in 2004-05. The center gets most of its financial support from The Robert Wood Johnson Foundation and is affiliated with Mathematica Policy Research Inc.