For the first time in 2015, monthly auction volume was down on a year-over-year basis. That’s according to the latest Economic Dashboard from the National Auto Auction Association released Monday.

Citing AuctionNet data, the report indicates that August auction volume was down 2.0 percent against comparable weeks of 2014. However, year-to-date volume is still up 6.3 percent, according to the report compiled by NAAA economist Ira Silver.

Auction volume had risen in each of the first seven months of 2015, including a 10.7-percent jump in January to get the year rolling, and an 8.3-percent gain in June.

Also released Monday was the latest Guidelines report from NADA Used Car Guide, a division of J.D. Power.

That report found that August auction volume for vehicles up to 8 years old (which it pegged at 291,000 units) was off 8 percent month-over-month and fell 6 percent year-over-year.

NADA Used Car Guide’s Jonathan Banks said in the report that a “portion of August’s pricing strength can likely be traced to lower auction supply.”

Interestingly enough, the Guidelines report notes that not a single model-year showed a month-over-month increase in August. In fact, the 2015 model-year group had been showing steady gains before August, but ended up down 10 percent from July.

Similarly, there was an average dip of 12 percent for model-years 2012 and 2013 units, while model-year 2014 volume fell 3 percent month-over-month and older model years showed a 5-percent dip, on average.

NADA Used Car Guide found that year-to-date auction volume for vehicles up to 8 years old is 6 percent ahead of where it was last year, having reached 2.81 million units through August.