WASHINGTON—Census surprise? The government provided new estimates Monday showing the U.S. population grew to somewhere between roughly 306 million and 313 million over the last decade, acknowledging uncertainty due to rapid shifts in immigration.
The estimates, which are separate from the official 2010 census count, are based on a review of birth and death records as well as calculations of new immigrants as of April 1, 2010. Demographers say the range of numbers offers a rough guide to the official 2010 results that will be used to apportion House seats when they are released later this month.
"For the first time, we are providing a series of demographic analysis estimates to more clearly demonstrate the uncertainty in these figures," said Census director Robert Groves.
The numbers show the nation's population ranged from 305.7 million to 307.4 million based on lower rates of immigration, which independent think-tanks such as the Pew Hispanic Center have said dropped off sharply recently due to the souring U.S. economy.
A mid-range estimate -- which in previous census reports have typically come within 1-2 percent of the final count -- puts the number at 308.5 million. Census estimates based on assumptions of higher levels of immigration place the nation's population between 310 million and 312.7 million.
In 2000, the official census count was 281.4 million.
No breakdowns were provided Monday for states or local areas.
The estimates also indicate:
--Hispanics accounted for all the growth in the youth population in the last decade. In 2000, Hispanics made up 17 percent of the U.S. population under age 20. They now represent somewhere between 22 and 25 percent of that age group.
--There were roughly 40.9 million to 41.7 million blacks in the U.S., based on a tabulation that includes Hispanic blacks. That would put the share of blacks at roughly 13 percent of the U.S. population.
--Without Hispanics, the number of young people in the U.S. would have declined between 2000 and 2010. Based on the estimates, the non-Hispanic youth population declined somewhere between 1.25 million and 2.9 million.
"The U.S. population is becoming more diverse from youngest to oldest and Hispanics are the driving force behind this youth diversity," said Kenneth Johnson, a sociology professor at the University of New Hampshire, who reviewed the numbers.
Monday's middle estimate of the total U.S. population is a bit lower than an earlier census calculation that put it at 309 million. That 309 million estimate, or various versions of it, has been used by outside analysts to project the distribution of House seats that show strong gains for immigration states such as Florida, Arizona and Texas.
John Long, who was chief of the Census Bureau's population division during the 2000 count, said that based on historical trends and decreased immigration, the latest estimates point to a final 2010 census tally that is "several million lower" than 309 million -- with high variability in states that tend to attract new immigrants.
He said the previous 309 million estimate is at least 1 million too high because of methodology changes in how the number is calculated when cities challenge the count. The estimates also may have failed to capture the most recent trends in immigration -- which included a sharp slowdown in illegal immigrants -- due to a time lag of more than one year in calculating the numbers.
"Each decade, census results have a way of surprising us," Long said. "These demographic analysis results indicate that the surprise may be in a downward direction. Most states will find that their population counts will be below what they expected."
The stakes are high. After state numbers are released later this month, the Census Bureau will begin to release population and race breakdowns for more local areas in February, triggering a process in which states gaining or losing House seats will redraw political boundaries.
Current projections by Election Data Services indicate that a dozen congressional seats affecting 18 states would change hands. They include four seats for Texas, two for Florida and one each for Arizona, Georgia, Nevada, South Carolina, Utah and Washington.
New York and Ohio are projected to lose two seats apiece, while eight states would lose single seats -- Illinois, Iowa, Louisiana, Massachusetts, Michigan, Missouri, New Jersey and Pennsylvania.
Kimball Brace, president of Election Data Services, said given the unpredictability in immigration suggested by Monday's estimates, Florida was likely to be more on the edge in gaining a second House seat. Also, because census estimates do not include U.S. military personnel and their families living overseas, he said a state with higher shares of Army posts, such as North Carolina, may prove to be an unexpected winner, as it was in 2000 when it beat out Utah for the last seat.
The census estimates released Monday -- known as Demographic Analysis -- have historically been used to assess the level of undercounts in the decennial census, which disproportionately misses children and black men. In recent censuses, they have also been used as one guidepost in the government's decisions whether to statistically adjust the census for known undercounts. Groves has ruled out making any adjustments in the 2010 census for purposes of reapportionment and redistricting.