Edmunds.com analysts discovered automaker incentives fell slightly in September as more and more 2013 models have hit the market.

According to the site’s True Cost of Incentives, the industry spent $2,227 per vehicle last month, down 3.1 percent from August and down 9.3 percent from September of last year.

Analysts indicated the decline ended a five-month streak of month-over-month incentive increases that began in April.

“This is the time of the year when inventories really start to see dramatic shifts in the proportion of vehicles from the upcoming model year,” said Edmunds.com senior analyst Jessica Caldwell.

“As demand builds for the new hot designs, car dealers don’t have to offer as much of a discount to move those vehicles off their lots,” Caldwell continued. "That’s why we recommend that car shoppers give extra consideration to some of the great deals on outgoing 2012 model year vehicles.”

Shoppers on the hunt for those outgoing models are likely finding that their choices are narrowing quickly.

Edmunds.com found that 67 percent of all new models sold in September were 2012 model year vehicles, down from 77 percent in August.

If historical patterns hold true, the site contends the industry can expect the 2012 model year mix to approach or fall below 50 percent in October.