While detailed results of the 2010 U.S. Census for Pennsylvania are due in days, the federal government today released estimates of 2010 population, and four counties in the region registered gains.

The Census Bureau estimated that Allegheny County had a net gain of 1,204 residents from mid-2009 through mid-2010, bringing its total to 1,220,510. That's still down 61,156 residents from the official 2000 census figure.

Similarly, the Census Bureau estimated that Beaver County gained 159 residents, Butler 821, and Washington 267 from mid-2009 through mid-2010.

Estimated population losers are Armstrong County, down 377; Fayette, down 625; Greene, down 179; Lawrence, down 524; Somerset, down 437; and Westmoreland, down 523 from one year to the next.

Christopher Briem, a demographer with the University of Pittsburgh's University Center for Social and Urban Research, said the results amount to "a very small tick" upward for the region. Nonetheless, he called the estimate "awfully important."

"I'm quite sure, given the numbers, that there's at least another year of net population migration into the region," following a similar trend from 2008 to 2009 in which more people moved into the region than out, he said.

"Our model has been showing that the population decline would be abating, would tick up to a small or moderate level of growth," he said. Why? The Pittsburgh area has suffered from somewhat lower unemployment, and somewhat firmer economic growth and income growth, than the nation as a whole, he said.

Though the coming flood of census data is almost certain to show overall population decline in most of the region's counties over the last decade, the estimates suggest that a better trend line may be emerging, he said.

First Published: March 7, 2011, 9:30 p.m.