HACKENSACK, N.J. — Real estate agents will collect a total of more than $56 billion in commissions this year, according to estimates from the Web site www.ForSaleByOwner.com. That's down from $65 billion last year and $68 billion in 2005, at the height of the real estate boom.

Commissions on home sales average 5.18 percent, the site estimated. On a home selling for $267,700, the average price nationally, that comes to about $13,900 nationwide — up from around $9,700 in 2000, before the big run-up in home prices. But because the total number of home sales has declined — to a projected 5.67 million nationwide this year from 7.1 million in 2005 — the total amount of commissions paid has dropped.

ForSaleByOwner, which provides Internet advertising for do-it-yourself home sellers, predicts that in a difficult real estate market, more sellers will try to go it alone in 2008 to save the cost of commissions. That's especially true, the Web site said, because commissions rose rapidly, along with house prices, in the first half of this decade.

The National Association of Realtors, however, says that in a buyer's market, many sellers are willing to pay for an agent's expertise.

"As a seller, you would want someone who has sold hundreds of homes and knows how to position your home competitively in the market," said Stephanie Singer, a spokeswoman for the NAR. In addition, she said, Realtors advise sellers how to prepare their homes for sale, negotiate the deal and provide other services.

According to the NAR, the number of "for sale by owner" sales has been trending down. About 12 percent of home sellers sold without using an agent this year, down from around 14 percent in 2003. In about half of those sales, Singer said, the owners sold to a friend, relative or neighbor. In those cases, she said, "you're not talking about homes entering the open market."

Singer also cited research that found that an agent can help a seller get a higher price — high enough to more than pay for the commission.

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