Edmunds.com has estimated that the average automotive manufacturer incentive in the U.S. was $2,742 per vehicle sold in March 2010, up $100, or 3.8 percent, from February 2010, but down $423, or 13.4 percent, from March 2009.

"Incentives helped lift sales to its highest level since Cash for Clunkers," stated Jessica Caldwell, Director of Industry Analysis for Edmunds.com. "And this month will be the highest ever for average combined incentive spending for Japanese automakers, including a record high month for Toyota."

According to Edmunds.com, combined incentives spending for domestic manufacturers averaged $3,413 per vehicle sold in March 2010, down from $3,463 in February 2010. From February 2010 to March 2010, European automakers increased incentives spending by $151 to $2,763 per vehicle sold; Japanese automakers increased incentives spending by $224 to $2,058 per vehicle sold; and Korean automakers increased incentives spending by $349 to $1,997 per vehicle sold.

Toyota set an incentives record in March averaging $2,256 per vehicle.

*Denotes a record high

In March, the industry's aggregate incentive spending is estimated to have totaled approximately $3.07 billion, up 49.4 percent from February 2010. Chrysler, Ford and General Motors spent an aggregate of $1.7 billion, or 54.8 percent of the total; Japanese manufacturers spent $922 million, or 30.5 percent; European manufacturers spent $262 million, or 8.7 percent; and Korean manufacturers spent $183 million, or 6.1 percent.

"April is typically a slower sales month than March, and we're already getting signal that some automakers will extend their incentives," continued Caldwell. "The question is will they be effective. The trend we saw in March was that incentives were very effective early in the month but far less so by month's end."

Among vehicle segments, large trucks had the highest average incentives, $4,290 per vehicle sold, followed by large SUV at $3,843. Subcompact cars had the lowest average incentives per vehicle sold, $1,294, followed by sport cars at $1,416. Analysis of incentives expenditures as a percentage of average sticker price for each segment shows large trucks averaged the highest, 12.6 percent, followed by large cars at 11.9 percent of sticker price. Premium sport cars averaged the lowest with 2.7 percent and sport cars followed with 4.4 percent of sticker price.

Comparing all brands, in March, Scion spent the least, $333 followed by MINI at $697 per vehicle sold. At the other end of the spectrum, Lincoln spent the most, $5,205, followed by BMW at $4,794 per vehicle sold. Relative to their vehicle prices, Saturn and Chrysler spent the most, 15.0 percent and 13.7 percent of sticker price, respectively; while Porsche spent 1.3 and Scion spent 1.9 percent.