Buyers closed on 37 percent more houses in King County in September than in the same month last year, according to statistics released Wednesday by the Northwest Multiple Listing Service.

But the year-over-year surge may reflect past weakness as much as current strength.

Sales volumes plummeted in mid-2010 — and didn't recover for several months — after homebuyer tax credits that were part of the Obama administration's economic-stimulus package expired.

Fewer houses sold in King County last September than in any September since at least 2004.

"It's very difficult to get an apples-to-apples comparison because of that," said Seattle land-use economist Matthew Gardner.

Last month's sales were down 2 percent from September 2009 — a month when the tax credit helped fuel sales — but up 12 percent from September 2008.

Fewer houses sold in September than August, but that is the typical seasonal pattern.

"Nothing too surprising here," Tim Ellis wrote in his Seattlebubble.com real-estate blog. "Same pattern as virtually every other year, sales dipping as we head into the fall and winter."

The median price of all King County houses that sold last month was $349,550, down 8 percent from the same month in 2010, but almost unchanged from August.

The median price has hovered between $345,000 and $350,000 since March. It fell to that level as sales of lower-priced "distressed" properties — bank-repossessed homes and "short sales" for less than the seller owes lenders — began to increase.

About one in five houses sold in King County in September was bank-owned, according to an analysis of listing-service data done for Washington Property Solutions, a short-sale negotiating firm.

Another one in 10 sales was a short sale.

Will prices rise anytime soon? The real-estate industry is facing some head winds "that are causing angst in the buying public," Gardner said. Those head winds include new restrictions on "jumbo" mortgages, proposals to require higher down payments for nonconforming loans and talk of eliminating the mortgage-interest tax deduction.

But the stability in median prices since spring is a positive sign, Gardner said, and he doesn't expect another big drop anytime soon.

In September sales increased — and prices fell — most precipitously year-over-year in Southwest and Southeast King County, where distressed properties are most prevalent.

Both areas saw double-digit declines in the median single-family home-sale price from September 2010. In Seattle and on the Eastside, in contrast, the drop was less than 5 percent.

The number of single-family listings was down 24 percent from last September countywide. "It's the sellers that are sitting on the sidelines, thinking it may make more sense to wait," Gardner said.

Inventory fell more steeply in Seattle and North King County, less steeply in Southwest King County, Southeast King County and on the Eastside.

In Seattle, the priciest neighborhoods — Queen Anne, Magnolia, Madison Park, Capitol Hill — also saw the steepest year-over-year drops in the number of listings. Lack of inventory is influencing the market in such close-in neighborhoods, brokers say.

On Queen Anne, "the price point between $600,000 and $700,000 — that price point seems to just absolutely fly off the shelf if the home has been priced right," said Chris Cooley, a broker at Windermere Real Estate's Queen Anne office.

"We've even seen multiple offers in that price range."

King County condo sales were up 33 percent from the same month last year, according to the listing service. But the median sale price, $195,000, was down nearly 19 percent year-over-year.

Single-family home sales in Snohomish County also rose nearly 30 percent in September from September 2010. The median price was $242,310, down 11 percent.

Eric Pryne: 206-464-2231 or epryne@seattletimes.com