As houses fell off the market more quickly and new listings slowed, sellers in Ada and Canyon counties raised their prices in May.

Ada County home sales rose 9.12 percent in the first five months of this year, compared with 2011, according to the Intermountain Multiple Listing Service. In May, about 22 percent fewer single-family homes were for sale. More sales were pending, and houses lingered on the market 11 fewer days than in May 2011.

Sellers got a confidence boost and raised their prices by double-digits. The median single-family home price was $179,900 in May, up from $158,777 in April. The national median asking price rose about 1.9 percent between those months, according to Realtor.com.

Thank new-home construction for the Ada County prices. Sales of newly built houses doubled, and prices rose 8 percent, compared with May 2011. But existing homes sold about 33 days faster than new ones.

That’s a reversal from 2011, when Ada County’s average single-family home was priced 10 percent lower than in the first five months of 2010.

But the county is still way behind 2006. In May 2006, the housing boom brought 3,195 homes to the market, and it was taking an average of 21 days to sell one of them. Six years later, 2,043 were listed, and it took 73 days to sell them.

Canyon County's supply also shrunk last month, by about 11 percent over May 2011. And prices were up. The median home cost $90,500 in May, up from $87,150 in April and $74,500 in May 2011. Houses stayed on the market about as long as they did in both April 2012 and May 2011.

Older homes may be driving Canyon prices. The majority of homes on the market between January and May were in the under-$90,000 price range. The average brand-new house in May was priced about $12,000 lower than in April, while existing homes commanded almost $9,000 more on average.

Audrey Dutton: 377-6448