Bay Area home prices in December soared 32 percent from a year earlier, the biggest such increase in a quarter century.

The median sales price for houses and condominiums in the nine-county region last month reached $442,750, according to according to DataQuick, a real estate information service. A year earlier the Bay Area median had been $335,500.

December’s median rose at the fastest year-over-year rate in all of DataQuick’s statistics, which go back to 1988. The price also was the highest since August 2008, when it had been $447,000.

“Prices are in the midst of bouncing off bottom right now, and nobody really knows what the trajectory of this bounce will be beyond this point,” said John Walsh, DataQuick president. “So far, supply has been a bottleneck, but as prices go up, more homes will be put up for sale.”

He noted that mortgage lenders currently are “swamped,” both by home buyers seeking new loans and by owners who wish to refinance.

“Rising home prices also mean higher appraisals, and tens of thousands of homeowners who couldn’t refinance half a year ago, now can,” Walsh said.

December sales numbered 7,832, a 7 percent increase from a year earlier and the 18th straight month in which sales have climbed year over year.

DataQuick analysts estimated that at least half the December price increase was due to a change in market mix. Sales shifted away from less expensive, distressed homes and toward mid-market and move-up properties.

Last month foreclosure resales and short sales together made up 34 percent of the market, compared to 52 percent a year earlier.

Absentee buyers, who are mostly investors, purchased nearly 26 percent of all Bay Area homes, the highest rate for data going back to January 1999. A year earlier they had purchased nearly 24 percent of the homes sold.

— Robert Digitale