DALLAS — Thanks largely to end of CARS, auto affordability took a significant hit in the fourth quarter of 2009, as it required 23 weeks of median family income to buy and finance an average-priced new vehicle, according to Comerica Bank's Auto Affordability Index. 

This marked a decline in affordability from revised third-quarter results, when the Index's best was 21.8 weeks.

Granted, fourth-quarter median family income climbed at roughly a 2-percent annual rate, and the average auto loan rate rates dropped to 3.47 percent, a decrease of 19 basis points.

However, vehicles were much more expensive.

Specifically, the average total cost of a new car was $27,000 during the final quarter of the year, a 6-percent increase compared to the third quarter.

"Affordability deteriorated in the fourth quarter, with most of the erosion almost certainly due to the expiration of the Cash for Clunkers rebate program," explained Dana Johnson, chief economist at Comerica Bank. 

"The effect of the program can be seen quite clearly in the bounce back that began in September in the average amount consumers spent on cars," Johnson continued. "A small rise in median family income and a small decline in financing rates offset only a small part of the sharp increase in car expenditures."