Wholesale auctions sold 9.8 million vehicles worth $100 billion in 2016 with the majority coming from dealer consignment, according to the National Auto Auction Association (NAAA). The association has been surveying its members for 20 years.

The reported 9.8 million units sold represented a 4.6% growth over 2015. The number of vehicles entering their auctions was also up, growing 2.3% to 17.7 million, according to NAAA.

"The survey results show the strength and depth of a mature industry that has demonstrated its resiliency," said NAAA CEO Frank Hackett. "I'm confident we'll continue to be a vital and growing part of our nation’s economy as we look forward to celebrating the auto auction industry’s 80th anniversary in 2018."

Dealer consignment accounted for 52% of the units sold in 2016, according to the survey. Fleet, lease, and repo — the organization labels this as Finance & Fleet — followed closely, accounting for 40.3% of unit sales. Manufacturer vehicles accounted for 6.5% of unit sales, and the remaining 1.2% came from other sources.

The average NAAA member auction operates on 78 acres, the survey found. In addition, the average auction facility operates eight lanes and employs 137 people with a payroll of $4.2 million. Of NAAA’s 342 member auctions, 252 responded to this survey.