Group health renewal rates may rise 8.5% for health maintenance organization plans and 9.4% for preferred provider organization plans in 2009.

Researchers at Milliman Inc., Seattle, have published those figures in a summary of preliminary results from a carrier survey.

Milliman tries to get “apples to apples” comparison figures by asking participants to provide rates for an employer with a specific demographic profile and a specific set of plan benefits.

Rate increases peaked at about 16% in 2002, Milliman says.

The aging of the population and an increase in chronic conditions such as obesity continue to push costs higher, researchers say.

Factors helping to hold increases down include increasing consumer cost awareness and “an economic downturn that may leave less money available for discretionary care for some people,” according to Doug Proebsting, a Milliman analyst who helped write the survey report.