Growth Cooling in D.C. Suburbs, Census Data Show

Valenza said that local figures have shown an annual population increase of about 1 percent in recent years. According to his estimates, the county's population grew from 853,000 in 2005 to 860,000 in 2006. "There's a lot of new construction going on here, and I don't think [the buildings] are standing vacant," he said.

In Anne Arundel, where census figures indicate a net loss of 97 people, county demographer Kavi Maddula said he had not yet done a population estimate for 2006. But he said that the county issued more than 2,300 building permits during the year, a figure that suggested to him that the population had grown.

"I haven't seen this data, but I would be surprised if those numbers were correct," said Maddula, who said his figures indicated that the county had 513,700 people in 2005. "If it were losing population, I don't think we would have the kind of activity that we've had in residential and nonresidential construction."

Loudoun's demographer, Jill Allmon, said her estimates also differ from the census figures. But she said the overall slowdown in growth indicated by the Census Bureau tracks with what county officials are seeing.

The number of new housing units, for instance, declined from 6,592 in 2005 to 5,803 in 2006.

Mike Gorman, owner of Oakridge Communities, which builds homes in Loudoun and Prince William, blames high housing prices, which in Loudoun have reached about $694,000 for a detached house and $426,000 for a townhouse.

"It's just expensive to live in Loudoun. The cost of a single-family home is expensive. The cost of a townhouse is expensive," Gorman said.

By contrast, Lang said, "you could move to Nashville or Atlanta or Columbia, South Carolina, and pay $300,000 for a right fine house. . . . So a lot of the people who are leaving Fairfax may just be bypassing Loudoun and heading straight for those places."

Staff writer Michael Laris contributed to this report.