The population of New York City has increased by only 2.1 percent since 2000, but the racial make-up continued changing significantly, according to the 2010 census released Thursday that stunned local politicians and could have implications for the city in Albany.

For the first time in five decades the city’s white population increased — by 0.6 percent — while the number of blacks decreased by 2 percent, WNYC’s analysis showed. The data also confirmed some noticeable trends: Asian population grew by 32 percent, and the number of Hispanics rose by 8.1 percent.

With the city's estimated population of 8.175 million, Mayor Michael Bloomberg said Thursday that he was concerned "there's been a significant undercount" and that the growth should be as much as 225,000 higher. Last year, the Census Bureau projected the city's population was about 8.4 million.

Bloomberg pointed to the negligible population increase in Queens of 1,300 people — numbers the mayor said likely reflected unwillingness of many immigrants to take part in the census and of illegal apartment conversions into multiple units.

Queens Borough President Helen Marshall, who also spoke at City Hall on Thursday, said she believed that despite the efforts to increase participation in the census, many immigrants may have decided not to fill out forms due to “privacy issues and language barriers.”

In Jackson Heights, Queens, Iban, an immigrant from Ecuador, who did not want his last name used, seemed to confirm Marshall's conclusions.

“I don’t like answering those types of questions,” he said of the census. “It’s not that it’s a bother. It’s just that it’s private.”

Another borough that saw only a modest increase in population — by 1.6 percent — was Brooklyn.

"I'm flabbergasted by these numbers," Brooklyn Borough President Marty Markowitz said. "I know they (the U.S. Census Bureau) made a big, big mistake."

He said he thought the increase in the number of Hasidic Jews alone would account for more than 1.6 percent.

For experts, such as John Mollenkopf, a political scientist and director of CUNY's Center for Urban Research, the census held surprises in other places — the city's demographic shifts for whites and blacks.

"The white population pretty much held steady, instead of declining, and the white population of New York City has been declining since 1950,” he said. "In a sense, whites and blacks have traded places in this decade, in terms of their population trajectories."

One of the neighborhoods where an influx of whites has been clearly visible is Harlem. Most interviewed residents there said they did not mind changes that happened over the last decade, but remained weary because they could already see some repercussions.

Tanya Gray, 40, who works as a healthcare worker and has spent most of her life in West Harlem, said she saw five families, her friends, leave the neighborhood over the last three years due to an increase in rent.

"Changes are squeezing some folks out of the neighborhood," she said. "It's not a racial thing. It’s a money thing."

Only a few blocks north, on the east side, in Spanish Harlem, according to the census data, the number of Asians increased significantly, contributing to the citywide increase of 32 percent. But the residents there said that they noticed a much smaller rise than those numbers indicate.

Qwmae Clancy, 33, who recently came back from Virginia Beach, Va., said the neighborhood looks pretty much the same as it did 10 years ago when he left.

"I didn't notice many changes," he said. "I didn't notice any increase in Asians."

The city's concerns about an undercount could affect New York’s balance of power in the Congress. The Census Bureau announced in December that New York’s House delegation will lose two seats, dropping to 27 due to a slow population growth of 2 percent relative to other states.

The mayor said that despite the effort to convince people to cooperate with the census, expected results were not accomplished and after-effects would be borne by New Yorkers.

"Our representation in both Albany and in Washington depends on how much, how many people we have," he said. "As does the amount of money for many programs that we get, both federal and state."

Steven Romalewski, who heads the Mapping Service at CUNY's Center for Urban Research, said previous assumptions that those two seats would come from the upstate area, might not be accurate: "I think, based on the numbers and the maps, it’s just as likely that New York City and Long Island could lose a seat."

Anna Sale, Cindy Rodriguez and Arun Venugopal contributed reporting. Listen to Arun Venugopal's report on Morning Edition: