According to data compiled by Edmunds.com, incentives on vehicle purchases averaged $2,902 in December 2008, the highest level in six years and up 18 percent from one year earlier.

Incentives began increasing in October and November and have posted peaks for three months as automakers struggle to overcome the lowest consumer demand in twenty-five years.

According to the Conference Board, a market information group, consumer confidence in the United States is at its lowest level since 1967, a fact clearly reflected in December's auto sales, down 35.6 percent from December 2007.

Jessica Caldwell, an analyst for Edmunds.com quoted in a report by Automotive News said, however, that the strategy isn't working. "They've been spending more and more money to try and entice anyone to come into a showroom. They're offering more and more money, but it's not really leading to any more sales."

In December, Toyota's incentives averaged $1,995, up 87 percent from 2007. Ford topped the list with average incentives of $4,029 per vehicle, followed by Chrysler at $3,667; General Motors at $3,661; Nissan at $2,251; and Honda at $1,218.

The highest incentives by vehicle segment are being offered on full-sized pickups with consumers getting breaks of as much as 16.5 percent of the sticker price.