Analysts at the NADA Used Car Guide say commercial-truck wholesale auction volume dropped "dramatically" during November, while incoming fourth quarter sales data appeared to look stronger than expected.

For the three most popular models sold at auction this year, the volume of 3- to 5-year-old units went from 254 in October to 95 in November. However, last month's drop was due to fewer auctions on the calendar and a typically less active purchasing environment going into winter, said Chris Visser, a senior analyst.

"For now, the tail is not wagging the dog," he said of auction performance so far this year. "It may be hard to believe, but looking at the year overall, and including all models, we estimate the three- to -five-year-old sleeper segment lost only 5% of its value from 2014 to 2015."

The report forecasts that the ever-increasing price of new commercial trucks will continue to keep an incrementally higher proportion of buyers in the used market, but supply is by far the more critical factor currently.

"We expect monthly depreciation to remain around 2% in the wholesale channel, and 1.5% in the retail channel through the winter," Visser said. 

NADA Used Car Guide is a division of J.D. Power & Associates.