Employers will see their medical plan costs rise an average of 13.5%, according to a new analysis by Aon Corp.

More demand for elderly services, as well as growing medical malpractice, technology and hospital costs are blamed for the projected price hikes. Aon said reasons for optimism were the rising use of generic drugs, as well as lighter use of prescription drugs. The findings are in Aon’s Fall 2004 Health Care Trend Survey, a semiannual publication.

Earlier in October, Hewitt Associates projected employer healthcare costs would rise an average of 11.3% in 2005. That easily outpaces the rate of inflation but is down from the 12.3% jump in 2004.

Consultancy Towers Perrin earlier in October projected employers would see an average rise in health costs of 8%, breaking a string of double-digit forecasts.