More than 22 percent of franchised dealers' used-car sales in the first quarter were certified pre-owned vehicles, according to Edmunds, which says these stores are feeling the pinch in their older inventory but see a flood of late-model supply.

There were 647,400 CPO sales in Q1, which was up a modest 0.1 percent year-over-year, according to the company’s latest Used Vehicle Market Report.

With franchised dealers selling 2.92 million used vehicles — a 0.3-percent decline — CPO had a 22.2-percent share of that market.

Overall, there were 10.2 million used-car sales industry-wide in the quarter, a 1.3-percent dip, Edmunds said.

“Fewer consumers trading in their existing vehicles on their new purchase could be side-stepping inventory from dealers,” the firm said in the report.

At least, older units.

Trade-ins had an average age of 6.4 years in Q1, which was steady with the prior year.

However, just 42.8 percent of buyers were willing to leave their current ride. A year ago, 45 percent were willing to do so.

“Lease returns will continue to flood the market over the coming years, while older used vehicles are poised for higher prices due to the supply shortage,” Edmunds senior analyst Ivan Drury said in a news release.

Used cars in retail transactions were a bit younger in the first quarter (4.4 years old, down from 4.5), but that change may become more pronounced.

“While the distribution still peaks at the 3-year-old age marker, it is anticipated that as the year progresses the market will see even more 3-year-old used vehicles being sold in the market,” Edmunds said.

A record 53 percent of used cars sold at franchised dealerships in Q1 were 3 years old or younger. It was at 52 percent in Q1 2016, having steadily increased each year included in the data set (which, in this report, goes back to 2012).

While retired rental vehicles will consistently have a presence in this age group, the latest growth is from off-lease, coming out of a time “when residuals were higher and leasing was an easy way to move more new cars,” Edmunds said.

Though both numbers are down year-over-year, the 31.7 percent lease penetration and 1.02 million leases originated in Q1 may suggest this trend is far from over.