The 2014 model-year crop of vehicles still dominates the volume at auction, according to NADA Used Car Guide, but here’s the catch.

Volume for this class actually decreased month-over-month in April, and future declines could be in store, the latest Guidelines report indicated.

“If last year's auction results for the 2013 model-year are any indication, we should see volume for 2014 models decline a bit more and then flatten out over the next few months,” NADA Used Car Guide’s Jonathan Banks said in the report.

Specifically, there were 63,400 units of 2014 model-year vehicles, compared to 68,600 in March.

Overall, auction volume last month showed about 327,000 units of vehicles up to eight years in age, beating year-ago figures by 7 percent, despite falling 4 percent from March. Year-to-date, auction volume has increased 7 percent, NADA reported.

The only two model-year groups that increased volume from March were the 2013 group (sales up 5 percent at 55,300) and the 2015 class (sales up 20 percent at 11,900), according to Guidelines.