Retail prices for medications used most commonly by Medicare patients rose almost 10% in 2013 – more than six times faster than the rate of inflation, according to an analysis by the AARP Public Policy Institute.

In 2013, “the average annual cost of drug therapy for prescription drugs, based on the AARP combined market basket used in this study, was over $11,000 per year,” according to the report In comparison, the average Social Security benefit was $15,526, the median income for Medicare beneficiaries was $23,500 and the median U.S. household income was $52,250.

Price increases for traditional and specialty brand prescription drugs rose faster than generics, eliminating any offset the declines in generic prices might have had.

The report examined drug prices from 2006 to 2013 for a combined market basket of 622 brand name and generic versions of traditional and specialty prescription drugs.

Of the 397 drugs that were on the market for all years, the average retail price increased 81%.