By Amy Zimmer
DNAinfo News Editor
MANHATTAN — The swath of the Upper East Side along Central Park has the most expensive real estate in the entire city. But it also has the highest percentage of vacant housing units, according to the 2010 Census.
More than 13 percent of the 36,700 units in the "Upper East Side – Carnegie Hill" neighborhood were vacant.
The vacancies, which increased 26 percent over 10 years, are an enigma in an area that saw a 3.8 percent decrease in the total number of housing units during that same span, though there is speculation that the total number of apartments dropped because many residents knocked down walls in multiple units to create mega-homes.
The area also saw a 3.9 percent decline in population, from 63,700 to 61,2007.
As census data continues to trickle in, it's too soon to know exactly what happened with this elite corner of the Upper East Side.
But it raises various questions: Were people at their homes in the Hamptons when census takers were in town? Did the financial crisis force people out of town, or at least into cheaper zip codes?
"We will be analyzing it," a spokesperson for the Department of City Planning said.
"It doesn't mean these houses are empty," said Jonathan Miller, a well-known real estate appraiser from Miller Samuel Inc., who is not a demographer but follows vacancy rates closely. He suggested that the numbers of high vacancies were because many of the residents own other homes elsewhere.
"In some strange way, the high vacancy rate suggests more affluence," Miller said.
The census does not account for pied-à-terres.
According to the census' website, a housing unit is vacant "if no one is living in it at the time [of the count] unless its occupants are only temporarily absent." It also states, "Units temporarily occupied at the time of enumeration entirely by people who have a usual residence elsewhere are also classified as vacant."
The Upper East Side's scenario differed from another exclusive Manhattan neighborhood with a 13 percent vacancy rate — Battery Park City. In that neighborhood, the vacancies could be accounted for because the total number of housing units increased to more than 24,000 from under 12,000, a 106 percent increase over 10 years. Other areas that had high vacancy rates — Harlem and Midtown South — also saw an increase in housing units.
The Upper East Side's neighbor, Yorkville, which has seen a flurry of construction over the past several years and had a 1.3 percent increase in the total number of units, only had a 5.4 percent vacancy rate.
But the area to its south, Turtle Bay – East Midtown, also had a nearly 13 percent vacancy rate.
Perhaps owners of townhouses off of Fifth Avenue — Mayor Michael Bloomberg's neighbors – didn't want to be bothered with answering census questions.
That's apparently what happened in the 14 square block census tract between Fifth and Park avenues from East 49th to 56th streets last April, when the city was entering its final census push.
That area — which is part of Turtle Bay and East Midtown — has a large number of foreign and other part-time residents in such buildings as the Olympic Tower, Park Avenue Place and Trump Tower and had the city's lowest response rate at 17 percent at the time, according to the New York Times.
"The big question is what about the vacancies," said Andrew Beveridge, Queens College sociology professor and demographic expert, who believes that the financial crisis had an effect on capping growth citywide, though he didn't know what was responsible for the vacancies on the Upper East Side.
"New York was growing, but after Lehman [brothers collapsed] it just stopped," Beveridge said of the bigger citywide picture. He had predicted a smaller population increase than projected by the city, which is contesting the results.
"I think the census might have counted properly," Beveridge said.