The median price of an Orange County home jumped 8.1 percent last month, the highest percentage gain in 31/2 years, MDA DataQuick reported Tuesday. The median price or price at the midpoint of all sales was $432,250.

Meanwhile, home sales barreled ahead at a 16.1 percent clip, with 2,528 residences changing hands.

On closer examination, however, the numbers may reflect a change in the mix of homes bought rather than an increase in their values.

Pricier homes are now finding buyers, market observers said, skewing the median price upward. Home values actually aren't up that much, brokers said.

You could have prices go down and have the median go up, observed Tony Hunthausen, an agent with RE/MAX Select One in Huntington Beach.

I don't think prices have gone down, he added. I think they've stabilized, and maybe bumped up a little bit.

One sign there's been an increase in pricier home sales: Sales were up 58 percent last month in Orange County ZIP codes with higher median prices the beach cities and the south-inland areas.

In quadrants with lower median prices the north-inland and central county ZIP codes sales were up just 3 percent.

There are more higher-priced listings that are closing, said Steve Thomas of Altera Real Estate, who produces bi-monthly reports on Orange County market trends.

Meanwhile, demand still exceeds supply for homes at the low end of the price spectrum, making it common to see as many as 20 to 30 bidders on a single home.

In the bottom ranges, we are seeing so much activity; and it's been hot for a long time we've seen some appreciation, Thomas said.

In addition, DataQuick reported:

Orange County's $432,250 median still is 33 percent below the June 2007 peak of $645,000.

The median also is down $4,250 from October the first month-to-month drop since April.

But the median rose 17 percent since the home price hit bottom at $370,000 in January.

The federal tax credit that had been set to expire Nov. 30 may have fueled November's 16.1 percent sales jump, some observers said.

Sales either had single-digit percentage gains, or even fell, in the months before November's surge.

The $8,000 credit has been extended through April.

Home sales also were up last month in 56 of Orange County's 83 ZIP codes, DataQuick figures show.

Sales doubled in 17 Orange County ZIP codes, while 25 ZIP codes had both sales and price gains last month.

On balance, however, sales still were anemic by historical standards.

Even though homebuyers purchased 2,528 properties in Orange County last month, the county averaged 3,900 sales a month before the housing slump.

Default numbers also remained high, although not as high as in recent months.

DataQuick reported that lenders seized 676 homes last month.

While down from October, that's up 6.8 percent from a year ago.

Lenders also filed 1,868 notices indicating that homeowners were three months or more behind on mortgage payments.

That's also down from October, but up 55 percent from a year ago.

This market is still really lopsided, said DataQuick President John Walsh. Foreclosures and short sales are huge factors. There's still not a lot of discretionary buying and selling outside the more affordable markets.

Century 21 Beachside agent Becky Sorensen said the wildcard for 2010 will be whether a new wave of foreclosures, or REOs, will hit the market.

The markets are going to get better as long as the banks don't flood the market with REOs, she said.