-- The Detroit Three automakers' share of "cash for clunkers" sales fell sharply, compared to foreign nameplates, in the final week of the $3 billion incentive program.

General Motors Co., Ford Motor Co. and Chrysler Group LLC sold 38.6 percent, or about 266,000 of the nearly 700,000 clunker replacements. That's far below their combined 45.3 percent share of 2009 auto sales.

The U.S.-based companies said they were hampered by a comparative shortage of small, fuel-efficient vehicles that buyers were seeking and that the Asian automakers provided.

"We started out hot and near the end, lean inventories had some effect," said GM spokesman Greg Martin. But, he added, "overall, it was a terrific program."

U.S. Transportation officials said Wednesday 690,114 voucher applications worth $2.877 billion were submitted by dealers, who'll be reimbursed up to $4,500 per vehicle.

After $100 million in administrative costs, that means about $23 million earmarked for car and light truck sales was unspent -- plus any funds left over from applications that didn't meet government requirements. Transportation officials said it's unclear what will happen to unused funds.

The Detroit Three's share of government-subsidized sales declined steadily as the program progressed.

GM finished with 17.6 percent of clunkers sales, behind Toyota Motor Corp.; Ford fell to 14.4 percent of total sales in the final tally, ahead of Honda Motor Co. with 13 percent.

The numbers were particularly gruesome for Chrysler. It ended with just 6.6 percent of clunker replacement sales, behind Nissan Motor Co. at 8.7 percent and Hyundai Motor at 7.2 percent.

Chrysler noted that it didn't produce any vehicles for nearly two months during its bankruptcy stay in early spring and summer, and had a 12 percent share in the early days of the program.

"The drop occurred in August when we had very low supply of our high mpg vehicles. We are building vehicles for customer orders and replenishing dealer inventories," Chrysler said in a statement.

Toyota was the big winner: Its Corolla was the No. 1 purchased vehicle, and its overall share of vehicles sold through the program was 19.4 percent -- more than 3 percentage points above its July market share.

"We had 25 models across the line that qualified" to replace clunkers, said Toyota spokesman Irv Miller. "We were in a pretty good position going forward."

As a result of the program, he said, Toyota made "some additional ordering" to keep its vehicle pipeline full, but declined to elaborate.

Ford's Focus FWD, at No. 4, and its Escape Hybrid FWD, at No. 10, were the only two vehicles produced by domestic automakers to crack the program's top 10 sellers.

The top 10 clunkers turned in, led by the Ford Explorer 4WD, were all domestic SUVs, pickups and vans.

It isn't clear yet how many customers shifted from U.S. to foreign vehicles, or vice versa.

Americans turned in about 580,000 light trucks and swapped about 300,000 of them for passenger cars.

A total of 84 percent of trade-ins under the program were light trucks, and 59 percent of new vehicles purchased were cars.The average fuel economy of new vehicles was 24.9 miles per gallon, compared with a trade-in mileage of 15.8 mpg, for an overall improvement of 9.2 mpg -- a 58 percent increase.

Michigan dealers' voucher requests totaled $132.4 million, the eighth highest among states. California was first at $327.6 million followed by Texas, New York, Florida, Illinois, Pennsylvania and Ohio.