A total of 3,918 existing single-family homes changed hands in the nine-county region last month, a big jump from 2,312 sales in January 2008, according to research firm MDA DataQuick of San Diego.

For the first time, more than half - 54.2 percent - of all homes sold in the nine-county region were bank-owned foreclosures. Their fire-sale prices drove the median sales price for existing homes down to $304,000, a nine-year low.

"Despite virtually no signs of home prices stabilizing anywhere, plenty of people have decided it is time to buy, simply because of the increased affordability," said Andrew LePage, a DataQuick analyst. "Through all this bleak news on the economy and jobs and home prices still eroding, plenty of people who sat out the frenzied stages of the market are deciding it may not pay to wait now."

The priced-to-move foreclosures devastated the market for new construction. Only 340 new homes were sold in the Bay Area in January, almost half of the 657 sold in January 2007, and the slowest January sales since DataQuick started keeping records 21 years ago.

Counties with the most foreclosures also had the biggest increases in sales volume and the biggest drops in median price. Contra Costa County, where 64.4 percent of all resold homes were foreclosures, saw sales almost triple to 1,075 in January, while the year-over-year median price plunged in half to $219,500.

At the other end of the spectrum, in San Francisco only 16.4 percent of sales were foreclosures and only 125 existing homes were sold - the fewest in any month since DataQuick began record-keeping in 1988. Counting in new homes and resold condos, 229 homes changed hands in San Francisco in January - also a record low.

Homeowners in San Francisco, San Mateo and Marin, where the distress levels are low, are likely opting to sit out the market turmoil as much as possible, LePage said.

"People who don't have to sell, won't," he said. "They're going to wait for a better day - for more robust demand, for financing to be more readily available."

The median price, which is the point at which half the homes sold for less and half for more, is affected by shifts in the composition of homes sold. A bigger number of lower-priced sales results in a lower median.

That could be seen in another statistic. Until the credit crunch hit in August 2007, almost two-thirds of Bay Area homes had mortgages above $417,000, DataQuick said. Last month, only 16.6 percent of purchase loans were above that mark.

Another telling detail: Resales of single-family detached homes hit record highs in affordable and foreclosure-ridden areas such as San Pablo, Richmond, Pittsburg, Antioch, Oakley and Fairfield, DataQuick said.

Many real estate agents describe bidding wars for distressed properties that rival those of the boom days - albeit at significantly lower price points.

"My strategy for short sales is to price about 10 percent below market," said Cindi Hagley, a Realtor with Windermere Welcome Home in San Ramon, discussing homes being sold for less than the owner owes on the mortgage. "They aren't always easy to sell because of the time to turn around but I'm getting offers that number in the teens; I had 22 offers on one listing."

Peter Harris, a Realtor with Bradley Real Estate in Novato, described the buyer competition over a four-bedroom, two-bathroom, bank-owned home in Rohnert Park last week.

"It came on at $219,000; it was well priced, which gets a lot of offers," he said. "When we wrote our offer, there were already 11 offers, then they wound up with 20, just in the first week. The Realtor said the bank wants everyone to come back with their highest and best offer. We came back with $230,000, which was well over asking and got beat out - we don't know what for, since it's still in contract."

Harris said that the quarter-million-dollar mark seems to be the dividing line for homes that attract a lot of interest. "Anything sub-$250,000 brings out a massive amount of buyers," he said.

Will the Obama administration's plan to rein in foreclosures and stabilize the housing market show up in statistical data soon?

"It will be really interesting if the combined industry efforts and the new government effort to stop the tide of foreclosures, if those are successful quickly, that will change the dynamics of the market," LePage said. "You won't see as much of this bargain bonanza in inland areas where prices have come down so much."

ACORN, the Association of Community Organizations for Reform Now, is starting a campaign to encourage families in foreclosure to refuse to leave their homes. C2

E-mail Carolyn Said at csaid@sfchronicle.com.

This article appeared on page C - 1 of the San Francisco Chronicle