WASHINGTON — The money-losing U.S. Postal Service guessed that TV cartoon character Homer Simpson and his family were twice as popular as Elvis Presley when it came to sales of commemorative stamps.

As Homer would say, "D'oh!" In a move that wasted $1.2 million in printing costs, the service produced 1 billion of "The Simpsons" stamps and sold 318 million.

The Postal Service inspector general in a report singled out the overproduction of stamps marking the 20th anniversary of the cartoon's run on News Corp.'s Fox network as an example of failing to align stamp production with demand.

"If the Postal Service can't address a simple matter such as determining how many commemorative stamps to produce, it shows they can't address the larger problems," Tom Schatz, president of Citizens Against Government Waste, said. "Unfortunately, even a small item can create larger problems."

The Postal Service earlier this month said it posted a loss of $5.2 billion in its third quarter and may lose $15 billion in the year ending Sept. 30. It has asked for Congress's help in cutting costs by eliminating a requirement to pre-pay for future retirees' health care and letting it stop Saturday mail delivery.

The service could save $2 million annually by ending overproduction of stamps that, like the Simpsons run, end up being destroyed when they don't sell, the inspector general said.

Mark Saunders, a Postal Service spokesman, declined to comment on the report or why the service produced so many Simpson stamps. "They want the response to the IG to speak for itself," he said in an interview.

Working from recommendations by a citizens' advisory board, the Postal Service produces about 20 commemorative stamp designs each year featuring historic events, geographic spots and pop- culture icons such as Homer Simpson.

Commemorative stamps are bought by collectors as well as people intending to use them to mail something. Most collectors buy stamps soon after they're issued, the report said, leading the inspector general to recommend limiting initial production of stamps and printing more if demand warrants.

The Simpson stamps, sold in 2009 and 2010, came in five designs featuring Homer, his wife, Marge, and children Bart, Lisa and baby Maggie. The stamps sold for 44 cents, 1 cent less than it costs now to mail a letter.

The inspector general criticized the process the service uses to decide how many stamps to produce, saying it's unscientific and too much of a judgment call. The July 23 audit was reported earlier by Linn's Stamp News, a weekly magazine for collectors.

"This process depends on manual procedures and the experience of one individual, which increases the risk for costly miscalculations," the report said. "Further, such errors may be detected if an independent review and assessment of production estimates were performed."

The Postal Service, in a response to the report, said it addressed the problem by creating the "forever" stamp, which can be used to mail a letter any time in the future. The Simpsons products were printed when most stamp values were fixed, meaning they could no longer be used by themselves to mail a letter after postal rates increased.

"The forever stamp has gone a long way in preventing overproduction," said Janet Sorensen, director of marketing and service in the IG's office and leader of the audit team that produced the report. "They need to get a better process for projecting the need, and they are implementing that type of process."

While the Simpsons stamp was the most overproduced during 2009 and 2010, the service also produced more stamps that it sold in those years featuring the lunar new year, civil rights movement figures, Zion National Park, Supreme Court justices, historic U.S. flags, film director Oscar Micheaux and a Christmas stamp showing an angel with a lute.

The inspector general probe found no instances during 2009 and 2010 in which there was more demand for commemorative stamps than supply.

The best-selling commemorative issued by the Postal Service was a 29-cent stamp issued in 1993 on what would have been Presley's 58th birthday. A Marilyn Monroe stamp issued in 1995 for 32 cents was another top seller.

Stamps issued in March featuring the cherry blossom trees ringing Washington's Tidal Basin oversold initial expectations and were reprinted, Saunders said. Other stamps that sold more than their initial print runs were the 1997 Bugs Bunny series and a 2010 series featuring animal shelter pets, he said.

The Postal Service has cut stamp production in line with falling demand for first-class mail, which includes letters and bills. It printed 21 billion stamps in the 2011 fiscal year. costing $43 million, down from 29.7 billion stamps. costing $56 million. in fiscal 2009, the report said.

First-class mail volume continued to decline in the quarter ended June 30, falling 3.5 percent compared with a year earlier, as people and businesses shift to e-mail and electronic transactions.