The amount of vehicles in auction that are 5 years old or newer increased 0.3% year-over-year in June, according to J.D. Power's July 2019 Used Car and Light Truck Guidelines.

While the month's gain was relatively small, gains through the rest of the year have set 2019's year-to-date auction volume 5.2% higher than where it was in the same time in 2018.

Much of this volume increase in the used space has been driven by SUV segments, according to J.D. Power. This trend is expected to continue as more SUV segment vehicles are sold in the new-vehicle segment — which will eventually make its way to the used side.

Compact SUVs have been a big volume driver, as year-to-date volume for the vehicle segment has increased by 25.6%; SUV volume has increased 14%.

Truck segments currently account for 52% of the volume share at auctions while car segments represent 48%.

For a long time, cars held a majority market share in the auction market, but market share has been skewing in favor of trucks since 2018.