With Memorial Day Weekend unofficially starting summer and vacation season, Black Book noticed somewhat sleepy auction lanes last week and expects more of the same this week.

But there are some interesting trends emerging that could affect the shape of the wholesale market as the temperatures continue to rise.

“Many buyers seem to still be supplementing their auction purchases with direct-from-consumer purchases,” Black Book analysts said in the weekly Market Insights report released Tuesday.  “Now there are companies with a business model of purchasing directly from consumers and selling through auction lanes, taking out some of the legwork for companies that may not have the time or resources to do it themselves.

“As we head towards the summer months, closed sales are expected to remain a popular means for OEMs to get available inventory to franchise dealerships, leaving others to compete for the picked over vehicles, at least until new-model-year launches are underway,” they said.

As it stands, the last full week of May showed wholesale prices increasing, albeit at a slower clip, Black Book said.

Overall, prices for the week ending Saturday were up 0.12%, compared to a 0.20% gain the week ending May 21.

Car segments were up 0.15% last week, versus a 0.37% rise the prior week. Trucks and SUV values were steady in their increase, rising 0.10%, compared to a 0.11% uptick the previous week.

Of note, all luxury segments showed declines, Black Book said. Premium sporty cars were down 0.49%, prestige luxury car values fell 0.18%, luxury car values were down 0.31% and near-luxury car values fell 0.13%.

Subcompact luxury crossovers were down 0.14%, compact luxury crossover/SUV values were down 0.08%, midsize luxury crossover/SUVs fell 0.03% and full-size luxury crossover/SUV dropped 0.48%.

Premium sporty cars, which had the most significant decline, have seen their values decrease for 25 straight weeks, Black Book said.