So much for the theory that rising wholesale volume would cause used-vehicle prices to soften — or even crash, as some doomsday observers feared.

The Manheim Used Vehicle Value Index climbed to a new record high in May as analysts determined wholesale used-vehicle prices (on a mix-, mileage- and seasonally adjusted basis) rose 2.6 percent month-over-month. The movement brought the index reading to 127.9, which is a record high and represented a 2.8-percent increase from a year ago.

The previous index high came last September when it was 126.9.

“The May index result challenges concerns that increasing wholesale supplies from near peak off-lease volumes and rising rental volumes would lead to rapidly declining used-car values. Indeed, the opposite appears to be happening,” new Cox Automotive chief economist Jonathan Smoke said in commentary that accompanied the latest index update.

“Higher commercial volumes at auction are providing the used vehicle market with quality and choice that offers a compelling value to consumers,” Smoke continued.

“Dealers responded to the consumer demand for used vehicles by purchasing the most vehicles at Manheim for the month of May since 2008,” he went on to say. “Year-over-year growth in sales outpaced the growth in inventory, which helped result in the record high index value. A slightly younger mix of vehicles also likely contributed to the record index level.”

Looking deeper at the six vehicle segments Manheim tracks for its update, analysts spotted May prices for pickups and vans helped to lead the charge to the new index record as they rose 9.1 percent and 7.3 percent, respectively, on a year-over-year basis.

Only the midsize car category dropped year-over-year, declining by 2.4 percent in May.

Within the off-rental market, Manheim determined the average price for rental risk units sold at auction in May dipped 2 percent year-over-year and 1 percent compared to April.

Analysts also mentioned SUV/CUVs accounted for 29 percent of rental risk sales in May versus 25 percent during the same month last year.  Compact cars’ share fell from 31 percent to 27 percent.

Manheim added that the average mileage for rental risk units in May (at 38,900 miles) settled 9 percent below a year ago.