The population of upstate New York declined by another 23,434 people between 2015 and 2016, while the population increase downstate slowed markedly below previous levels during the same period, according to the latest U.S. Census Bureau estimates.

During the 12-month period ending last July 1, the downstate region (New York City, Long Island and the lower Hudson Valley) gained a combined total of 21,540 people, less than half the region’s increase during the previous year. This brought the total downstate population to 13,465,661, an increase of 426,835 since the 2010 census, while the combined population in 50 upstate counties stood at 6,279,628, a decrease of 59,648 people since 2010.

Because upstate lost slightly more people than downstate gained during the latest 12-month period, New York’s statewide population declined for the first time in a decade in 2015-16.

As shown in Table 1 below, all but two counties (both upstate) have lost population due to domestic migration—the movement of residents to other states and across county lines. The “natural increase” in population from childbirths minus deaths, plus an influx of immigrants from foreign countries, more than offset the downstate domestic migration loss.

Highlights of 2016 Census Bureau estimates for New York

(See Tables 1 and 2 for more details)

• Population loss is accelerating in Suffolk, New York’s largest county outside New York City. Driving the trend: higher domestic migration (up 15 percent in the past year), a lower birth rate (down 4 percent) and an increase in the death rate (up 4 percent) among county residents. Suffolk, one of the nation’s fastest growing suburbs for much of the post-war era, ranked fifth on the Census Bureau’s list of “Top 10 Largest-Declining Counties or County Equivalents” in the 2015-16 period, trailing only Cook County, Ill. (Chicago), Wayne County, Mich. (Detroit), Baltimore city, Md., and Cuyahoga County, Ohio (Cleveland).

• Brooklyn, Queens and the Bronx, in that order, have experienced the state’s largest overall population increases since 2010, driven mainly by large natural increases. Outside New York City, the largest percentage increases in population have occurred in Rockland, Saratoga and Tompkins counties.

• The biggest population losses since the last decennial census have been in upstate rural areas: Delaware, Hamilton, Schoharie and Tioga counties.

• New York (borough of Manhattan) and Queens have been the only New York City counties with gains from net migration (domestic plus foreign) since 2010. Outside the city, net migration increases were estimated for seven counties: Albany, Erie, Nassau, Ontario, Saratoga, Tompkins and Westchester.

• Ontario and Saratoga have been the only counties to experience positive domestic migration, meaning they attracted more new residents from the rest of the nation, including other New York counties, than they lost (see map below).