The cost of health insurance in the U.S. jumped this year, with average annual premiums for a family plan surging 9 percent, to more than $15,000, a new study has found.

That increase compares with a 3 percent rise last year, according to the survey released Tuesday by the Kaiser Family Foundation and the Health Research & Educational Trust.

Premiums for single coverage increased 8 percent, to $5,429.

The unexpectedly high increases come at a bad time for many workers, already buffeted by a stagnant economy and scant wage increases.

“This year’s 9 percent increase in premiums is especially painful for workers and employers struggling through a weak recovery,” said Kaiser President and CEO Drew Altman.

“The open question is whether that’s a one-time spike or the start of a period of higher increases,” Altman said in a New York Times article.

Premiums this year increased significantly faster than workers’ wages (2.1 percent) and general inflation (3.2 percent), the study said. Since 2001, family premiums have jumped 113 percent, compared with 34 percent for workers’ wages and 27 percent for inflation.

Employers continue to pay the largest share of health insurance, as workers paid an average of $921 toward the premium for single coverage and $4,129 for family plans, the survey found.

Although many benefit analysts say the federal health reform law’s requirements played only a small part in the premium increases, the results could provide political fodder for both supporters and opponents of the law, Kaiser Health News reported.

Many factors drive premium growth, the main one being actual spending on medical care, KHN pointed out. That would include jumps in prices charged by hospitals and doctors and growing use of expensive new drugs and medical technologies.

Businesses may have reacted to these cost increases by freezing retirement account contributions or giving a flat wage or smaller pay increase to their workers, said Helen Darling, CEO of the National Business Group on Health, which represents large employers, in an Associated Press/USA Today article.

Employees “basically are giving their pay raise to the health system,” said Darling, who was not involved with the Kaiser study. “It’s really bad news.”

The 13th annual Kaiser/HRET survey was conducted from January to May and was drawn from the responses of more than 2,000 large and small businesses.

It estimated that employers added 2.3 million young adults to family health insurance policies, a result of the health reform law’s provision that allows children up to age 26 to join their parents’ plan.

There may be better news on health insurance costs next year. Benefit consulting company Mercer said recently that an employer survey it did shows the 2012 costs will rise by 5.4 percent, the smallest amount since 1997, the AP story reported.