The Manheim Used Vehicle Index rose in September for the fourth month in a row, capping its strongest quarterly gain since the middle of 2011, Tom Webb, Manheim's chief economist, said Monday.
But prices are expected to "moderate" over the next year, he added.
Last month, the index stood at 122.8, up from 122.3 in August and 120.7 in September 2012. Industrywide wholesale prices for the quarter rose 2.2 percent from the previous quarter.
The index measures used-vehicle price changes and is adjusted for vehicle mix, mileage and time of year.
Used-vehicle prices typically soften in the autumn, but Webb said he wasn't surprised at their strength in September given that dealers went into the month with lower new-vehicle inventory and shortages of some key models.
"Statistically speaking, there is no greater determinant of used-vehicle values than the number of new units that sit on dealerships' lots," he said today during the company's quarterly conference call with analysts and journalists.
Webb said he expects new-vehicle inventory volumes to build and the number of off-lease vehicles returning to the market to rise, putting downward pressure on used-vehicle prices. But he also expects used-vehicle demand, buoyed by the availability of credit, to remain strong in 2014, which will help support used-vehicle values over the coming year.
Among vehicle segments reported by Manheim in September, used pickups registered the largest price gains with an increase of 7.4 percent from September 2012. In the same period, prices of used luxury cars dropped the most, 1.4 percent.