Long Island showed modest population gains from 2012 to 2013, though Suffolk County's anemic growth was eclipsed by Nassau County, according to U.S. Census Bureau estimates released Thursday.
The estimates showed Suffolk's population rose by 1,780 from July 1, 2012, to July 1, 2013, for a total population of 1,499,738. Nassau's increased by 3,863 during the period, for a total population of 1,352,146.
Suffolk's gain in 2013 was a rebound from a year earlier, when the revised estimates showed it lost about 1,600 people between 2011 and 2012. The Island had an overall population gain in 2012 because of Nassau's increase of more than 3,000 people.
Suffolk's sluggish gains in recent years are a change from the century's first decade, when the county's population grew 5.2 percent, compared with Nassau's 0.4 percent increase during that period.
The primary culprit, demographers said, is people leaving Suffolk for elsewhere in the nation, what the bureau calls domestic migration.
There are "more people leaving Suffolk than coming in," said Jan Vink, a researcher with Cornell University's Program on Applied Demographics, which is an affiliate of the Federal-State Cooperative on Population Estimates.
However, what Vink called "the natural increase" -- more births than deaths -- kept the county in the plus column for growth despite the outflow.
International migration overcame domestic migration losses in Nassau, but not in Suffolk. International migrants to Nassau from July 1, 2012, to July 1, 2013, numbered 3,510, while the county saw a loss of 1,834 domestic migrants. Suffolk had 3,949 international migrants during the same period, but saw 5,791 domestic migrants leave.
Vink said Nassau's growth may be a reflection of its proximity to New York City.
Ben Bolender, a Census Bureau demographer, said both counties saw far larger losses of people moving to other parts of the nation in the mid-2000s.
"If you look at the years 2000 and 2010, yes, Suffolk grew," Bolender said, "but when you look at 2005, 2006 and 2007, Suffolk lost population, again because of domestic migration."
For example, in 2005, just over 14,000 people left the county, and the number jumped to nearly 16,000 in 2006, he said. In 2007, Suffolk's domestic migration losses were an estimated 13,800.
Nassau saw large domestic migration losses in the mid-2000s as well -- about 15,000 in 2005 and 17,000 in 2006 before dropping to about 12,000 in 2007.
Commenting earlier this year when population estimates for states were released, Kenneth Johnson, senior demographer at the University of New Hampshire's Carsey Institute, said the recession -- which officially ran from December 2007 to June 2009 -- "slowed out-migration" from New York.