Census: 308.7 million people live here

NEW YORK (CNNMoney.com) -- The population of the United States grew 9.7% to 308.7 million people over the past decade -- the slowest rate of growth since the Great Depression -- the Census Bureau reported on Tuesday.

In the 1930s, the population grew by just 7.3%. Comparatively, the nation added 13.2% more residents during the 1990s. (See CNN's special Census coverage.)

This is the first time the Census Bureau has released data from the population surveys filled out earlier this year. And the counts include everyone -- not just citizens or legal immigrants.

"The mandate is to count everyone living in the United States," said a Census Bureau spokeswoman.

The U.S. Constitution charges the Census Bureau with the task of counting residents every 10 years to track population shifts in the country. And the law requires the Census to report the official population counts -- both national and by state -- to the President before Jan. 1. The numbers are used to apportion Congressional seats.

"The Census forms the backbone for our political and economic systems for years to come," said U.S. Commerce Secretary, Gary Locke.

The results were seen as a blow to Obama and a win for Republicans because most of the states losing electoral votes and seats in the House of Representatives, such as New York, Massachussetts and New Jersey, lean toward or are heavily Democratic while many of the ones gaining seats, such as Texas and Arizona, are Republican strongholds.

The winners are concentrated in two of the nation's four regions: Both the West and the South experienced double-digit growth rates, 14.3% in the South, already the most heavily populated region, and 13.8% in the West. The Midwest rose 3.9% and the Northeast grew 3.2%

Nevada was the fastest growing state over the decade, followed by Arizona and Utah. Michigan was the big loser, with Rhode Island, Ohio and Louisiana also lagging badly.

The five biggest states are California, ranked first with more than 37 million residents, followed by Texas, New York, Florida and Illinois. (Table of state population is at the bottom of this story.)

The least populous state, with fewer than a 600,000 residents, is Wyoming. Vermont, North Dakota, Alaska and South Dakota round out the bottom five, all with fewer than a million people.

Census Bureau director Robert Groves said that natural replacement accounted for about 60% of the growth this past decade while immigration made up the remaining 40%. But growth slowed dramatically because the birth rate fell during the decade and fewer people moved to the U.S.

The country's fertility rate is nearly 2.1 children per woman, just about the natural replacement rate, according to data from the United Nations World Population Prospects. That is down from the baby-boom years, when it hit a peak of 3.7, but above most developed countries.

And the recent recession resulted in a slowing immigration rate, according to Carl Haub, a demographer with the Population Reference Bureau, a Washington-based non-profit. "The population growth rate drop is largely because of a couple percentage point dip in immigration," he said.

"India's technicians and engineers who came here sent word back home that it's hard now," Haub added. "The IT industry is not the golden goose it's been in the past."

Despite the slowdown, the nation's growth rate is much higher than most developed countries. The populations of Japan and Germany, for example, are in decline, while France and the United Kingdom are growing at a rate of 5% per decade.