A ceaseless barrage of new brand car ads on TV and radio didn't help matters. That siren song of accelerating engines lured people into dealerships, where liberal lenders encouraged them to check their wallets — and their common sense — at the door.

A first factor in the U.S. auto market's update deterioration was the people who took out car loans they couldn't afford. While being upside down on a car loan is nothing new, in 2010, 21.8 percent of Americans who bought a new car still had an average of $3,789 in negative equity on their trade-in, according to Edmunds data.

How much car you can really afford? Our new affordability calculator gives you a price range for shopping based on your desired monthly payment.