PROVIDENCE – The average family health insurance premium offered by Rhode Island employers cost $13,363 last year, ninth-most in the country, according to a study released last week by The Commonwealth Fund, a nonpartisan research group.

The average family premium rose 41 percent, from $9,460 to $13,363 between 2003 and 2008, more than the average increase nationwide of 33 percent.

In addition, the average health insurance premium for a single employee in Rhode Island rose 32 percent, from $3,725 in 2003 to $4,930 last year, compared with a 26 percent increase nationwide to $4,386 last year.

By 2020, health premiums in Rhode Island will average $9,576 for single workers and $25,906 for families if medical insurance inflation continues to increase at its current rate, the study said.

Nationwide, the average family premium for an employer-sponsored plan in the United States was $12,298 last year. Rhode Island was one of 20 states where premiums for family coverage cost more than the national average.

The average family premium increased 119 percent from 1999 to 2008 in the U.S., and is on track to rise another 94 percent to $23,842 by 2020 if present trends continue, the report found.

“These rapid premium increases aren’t sustainable for families or employers,” Commonwealth Fund President Karen Davis said in a statement. “If we craft patient-centered reform that focuses on improving quality and efficiency and bending the cost curve, the insured in every state stand to benefit. We could assure coverage and, over time, make more money available for wages, retirement and other family needs.”

The six New England states had some of the most expensive insurance premiums in the country last year, the study found.

Massachusetts’ family health insurance premiums were the most expensive nationally at $13,788, up 40 percent since 2003. New Hampshire ranked fourth highest, followed by Connecticut at sixth highest, Maine at 10th highest and Vermont at 11th highest.

“With health spending projected to double if we stay on our current path, middle and lower income families are at high risk of losing their coverage or facing long-term stagnant incomes,” Cathy Schoen, the report’s lead author and a senior vice president at The Commonwealth Fund, said in a statement.

“Employers and employees share premium costs, but we know that take-home pay and retirement savings are being sacrificed to maintain health benefits,” she said. “Reforms that slow the growth of health care costs could go a long way toward health and financial stability for working families.”

The Commonwealth Fund report suggested a number of reforms, such as limits on health insurers’ costs and profits and changing the way providers are compensated, that could save the nation $2 trillion to $3 trillion, or an average of 1 to 1.5 percentage points off annual projected costs, over the next decade.

President Barack Obama has emphasized the need to control skyrocketing medical costs as part of his push for health care reform, which Congress will take up again next month when it returns from its summer recess after Labor Day.

Additional information is available at CommonwealthFund.org.