Used car prices have run up 20% since January after falling for much of 2009 and 2010, researcher Kelley Blue Book said Monday. And Manheim Consulting, an arm of one of the nation's largest wholesale used car auction companies, says prices are being bid higher than at any time since it started keeping track in 1995.

For example, a 3-year-old Ford Explorer sold for twice as much last month — $14,200 — as a 3-year-old Explorer sold for in 2007, Kelley Blue Book says.

For dealers, getting hold of good used cars is an increasing challenge. "It's tougher to find cars for people who are ready to buy than a year ago," says Jerry Seiner, who has General Motors, Kia and Nissan dealerships in the Salt Lake City area.