The newer, low-mileage used vehicles carry high prices rivaling those of new ones, and the situation will likely worsen.
"High levels of lease returns coupled with increasing stringent mileage limits will feed an expanding pool of low-mileage used-vehicle inventories that have proven to have a limited buying audience," Edmunds said.
Ivan Drury, senior manager of analytics development at Edmunds, said older used vehicles with more mileage and lower prices are selling faster than low-mileage newer models. In the third quarter, 2010 models sold in an average 34 days, 2013s in 42 days and 2016s in 51 days, Edmunds data showed.
Next year's influx will look different, Drury said. He expects 2018 off-lease returns to be less car-heavy and grow 13 percent from 2017.
Drury's estimates combined retail sales and lease penetration for each of Edmunds' light-vehicle segments, subtracting wrecked vehicles and those bought by lessees at the end of the lease rather than returned.
The 2018 differences are dramatic, ranging from a 20 percent decline in subcompact cars to a more than doubling of compact truck returns to 37,000.
The three luxury SUV segments — entry, midrange and premium — will each jump more than 30 percent next year. So will compact crossovers, rising 31 percent or 120,000 vehicles to more than a half million.
Individual light-truck segments all will grow in 2018. Off-lease pickups will grow 30 percent to 279,000 vehicles, SUVs 27 percent to 561,000 and crossovers 25 percent to remain the largest segment at 939,000.