Growth in the health insurance premiums charged by companies including UnitedHealth Group Inc. and WellPoint Inc. has slowed to 4.5 percent this year, less than half of 2011's rate, the Kaiser Family Foundation said.

The average cost for a family plan obtained through an employer jumped to $15,745 this year, from $15,073 in 2011, when premiums rose 9.5 percent, the Menlo Park, California-based research group said today after surveying more than 2,000 companies. Premiums, a cost typically shared by employers and employees, have doubled in the past decade, three times the gains in wages and inflation, according to Kaiser.

"This year's 4 percent increase qualifies as a good year, but it still takes a growing bite out of middle-class workers' wages, which have been flat or falling in real terms," Drew Altman, president and chief executive officer of the foundation, said in a statement.