A plunge in the amount of properties for potential buyers to look at also put a dent in sales, with units sold in D.C. down 12 percent from a year ago, and down 8 percent in Arlington County.

WASHINGTON — As the spring housing market kicks into high gear, house hunters in the Washington area will have even less to look at in some of the region’s most popular areas this year.

Long & Foster says inventory, or the number of houses and condos on the market, in D.C., Loudoun County and Arlington County was down 22 percent in March compared to a year ago.

Fairfax County, Prince William County, Montgomery County and Prince George’s County all saw a double-digit decline in year-over-year inventory.

Lack of properties for potential buyers to look at also put a dent in sales, with units sold in D.C. down 12 percent from a year ago, and down 8 percent in Arlington County.

Tight supply is not hurting prices.

The median price of a home that sold in D.C. in March was more than $555,000, up 3 percent from last March. Arlington’s median selling price last month was $565,000, up 11 percent.

“A ‘perfect storm’ of market conditions is compounding an ongoing inventory crunch,” said Larry Foster, president of Long & Foster.

“Builders’ margins are squeezed by rising labor and materials prices, so they are not meeting demand for entry-level and move-up homes. Would-be sellers of existing homes, many of whom refinanced at low interest rates, are reluctant to list their homes because they aren’t finding the selection of properties they want to move into,” he said.

Prince George’s County remains the region’s most affordable housing market, with a median selling price of $270,000 in March, less than half the median price in Arlington.

A recent Affordability Score report from the National Association of Realtors says just 42 percent of median income households in the Washington region can afford to buy a median priced home.