Large employers in Rhode Island have recently been restricting which of their employees qualify for health insurance, and these moves are the chief reason why the number of uninsured people has been rising steadily since 1999.

The finding, in a first-of-its-kind report today from the state health insurance commissioner, casts a new light on the debate over the uninsured, which has focused on helping small businesses that can’t afford premiums.

The new study shifts the spotlight to large businesses, which employ about two-thirds of the work force. It found that these employers (with more than 50 employees) continue to offer health insurance at the same rate as in the past, but they have been controlling premium costs by limiting eligibility. For example, employees might not be eligible if they work fewer than a certain number of hours or if they are newly hired.

As a result, Rhode Island compares poorly with Massachusetts and the nation in terms of employer-sponsored health insurance. In 2004, 69 percent of Rhode Island workers were eligible for insurance through their employer, compared with 77 percent in Massachusetts and 78 percent nationally.

Now, about 1 in 8 Rhode Islanders under age 65 has no health insurance. At the beginning of the century, less than 1 in 10 were uninsured. If this trend continues, the report estimates that 1 in 5 people will be uninsured by 2010.

Studies have shown that uninsured people are less likely to go to the doctor or dentist, have poorer health, and impose considerable costs on the hospitals that care for them when they fall ill. Most uninsured people have jobs and low incomes.

Today’s report from the Office of the Health Insurance Commissioner is the first statistical portrait of who is uninsured in Rhode Island, and why. It combines data from the U.S. Census Bureau with the results of the Rhode Island Health Interview Survey, a telephone survey last conducted in 2004.