​​New York State’s surprisingly large population gain since 2010 was concentrated in New York City and its inner suburbs, according to the local-level 2020 Census data released today—pointing to a further shift of Assembly and Senate seats from upstate to downstate in the coming round of legislative reapportionment.

The Census Bureau’s statewide headcount, released in late April, had pegged New York’s 2020 total resident population at 20,201,249—a marked turnaround from the stagnant trend suggested by annual estimates since the last census in 2010. Compared to the 2010 statewide total for New York, the 2020 count showed a population gain of 823,147, or 4.25 percent—the Empire State’s second fastest growth rate since the 1960s (it was 5.5 percent during the 1990s), and more than twice the 2000-2010 increase of 2.1 percent.

The decennial census exceeded the Census Bureau’s 2019 estimate by a whopping 762,190 people, a difference of 3.9 percent. In percentage terms, the only state with a bigger change from its 2019 estimate was New Jersey, whose 2020 census population count was 4.6 percent higher than its estimate for a year earlier.

With today’s release of the Census Bureau’s localized block-level data, we now know where all that population growth was concentrated, as illustrated on a countywide basis by the map below.

The total population of the 12-county downstate region increased 828,346, three quarters of which consisted of New York City’s addition of 629,051 residents over the 2010 Census count. Population declines were reported for 39 37 of the 50 upstate counties, mostly rural and suburban areas, while increased headcounts well above previous estimates were reported for the largest urban counties—starting with Erie County, which added 35,196 residents, according to the Census Bureau.

This spreadsheet lays out sortable 2010 and 2020 totals for counties, cities, towns and villages in New York, as calculated by the Empire Center based on a master file of block data made public by the Census Bureau today.

The immigrant factor

The Census Bureau’s so-called “intercensal” annual estimates are based on highly reliable government sources including birth and death records, federal income tax returns, and universal federal Medicare enrollment of the over-65 population. Thus any difference between estimates and census counts is likely to consist of individuals not counted by those other records—primarily foreign immigrants, both legal and illegal.

The 2020 Census count was uniquely tricky—no doubt featuring a good deal more guesswork and outright fudging than usual—because of the COVID-19 pandemic and resulting lockdown of normal economic and social activity. By April 1, 2020—the date to which the Census is pegged—many New York City dwellers already had temporarily moved to urban and rural areas. But no hint of a decrease is reflected in the city’s population count, which reflects permanent residency.

A further potential distortion in the data might have arisen by the pandemic’s impact on colleges and universities. The decennial census normally includes resident undergraduate and graduate students in the towns and cities where they live during the school year, in turn bolstering the count in those areas for legislative and congressional apportionment purposes.

New York has an exceptionally large post-secondary education sector, with 311 institutions enrolling more than a million students. SUNY’s four-year colleges alone have more than 200,000 students, mostly residing during the academic year at upstate residential campuses.

The Census data are supposed to reflect populations as of April 1—but by that date in 2020, college towns had been partially depopulated. Nonetheless, for example, the 2020 census reflects the first population gain in 70 years for the city of Buffalo—something that would be highly unlikely if based on a hard count of actual residency at Buffalo colleges and universities as of April 1, 2020.

Likewise, the data show a population growth of 3,450 residents (2.4 percent) for Syracuse, where Syracuse University has a largely residential undergraduate enrollment of 15,000. These and other numbers for communities with a large higher-ed presence suggest the Census Bureau derived its 2020 college campus and off-campus housing counts from the normal levels confirmed by the institutions in previous years, as opposed to actual levels in April 2020. But it leaves open the question of how many students sent home by their colleges ended up double-counted on their parents’ census forms.