Cash for Clunkers saw 700,000 old, mostly shitty cars traded in for shiny new ones, but it didn't actually impact the total number of vehicles on the road, since its terms dictated a new car had to replace the old.
The EPI instead cites a sales volume that was at its lowest point since 1982, the increased urbanization of the American populace (four out of five now live in towns) and the increased cost of owning a vehicle.
Since the country still has 246 million licensed cars, yet only 209 million licensed drivers, EPI expects this trend to continue, saying that America has reached "the saturation point for cars" and comparing it to Japan, where licensed cars peaked in 1990 and has since seen a 21 percent drop. EPI predicts the number of cars on American roads will drop 10% by 2020 as sales fail to return the 17 million annual level that was achieved between 1999 and 2007, saying that 10 to 14 million is a more realistic number. [EPI via The Guardian]