Sonoma County home sales accelerated in May, but it didn’t translate into a higher median sales price.

Buyers purchased 495 single-family homes last month, according to The Press Democrat’s monthly housing report compiled by Pacific Union International Vice President Rick Laws. That was up 12 percent from April and up 36 percent from May 2011.

Even so, the county’s median price fell 4 percent from April to $330,000. The median was down 7 percent from a year earlier.

The housing market this year is characterized by increased sales, stronger demand and low inventory, real estate agents said.

But the growth in sales has been concentrated in the lower end of the market, especially for distressed properties known as short sales, where the home is sold for less than the amount owed on the mortgage. As a result, the sales of those less-expensive homes have pulled down the median price — the point at which half the homes sold for more, and half for less.

“The short sales are just going through the roof,” said Mike Kelly, an agent with Keller Williams in Santa Rosa. He still expects the median price to rise later this year.

The county’s median hit a record high of $619,000 in August 2005 before tumbling to $305,000 in February 2009.

In contrast to the county, the Bay Area saw increases in both sales and median price in May.

Buyers purchased 8,810 houses and condos in the nine-county region last month, according to DataQuick, a San Diego real estate information service. It was the highest result for a May since 2006, when 9,935 homes sold.

The Bay Area median price last month rose to $400,000, up nearly 3 percent from April and almost 8 percent from a year earlier.

The year-over-year increase in Bay Area home sales was most pronounced in the higher price categories. Sales below $300,000 rose nearly 13 percent, but those over $500,000 shot up 24 percent.

“It’s not exactly a stampede, but people are starting to move off the housing market sidelines in numbers we haven’t seen in quite a while,” said John Walsh, DataQuick president. “And it’s not just first-time buyers and investors. There are more move-up buyers in mid- to high-end coastal counties.”

— Robert Digitale