WASHINGTON - Many states that posted big population gains in the 2010 census are now seeing their decadelong growth fizzle, hurt by a prolonged economic slump that is stretching into larger portions of the South and West.

New 2011 estimates released Wednesday by the Census Bureau are the first state numbers since the 2010 count, which found the nation's population growth shifting to the Sun Belt.

As a whole, the U.S. population grew by 2.8 million, reaching 311.6 million people. That growth of 0.92 percent was the lowest since the mid-1940s, hurt by fewer births and less immigration following the recent recession. From 2000 to 2010, the government previously reported the nation grew 9.7 percent, the lowest since the Great Depression.

"The nation's overall growth rate is now at its lowest point since before the baby boom," said Census Bureau director Robert Groves.

Washington grew faster than any state in the nation, climbing by 2.7 percent from April 2010 to July of this year. It was the first time the District led states in growth since the early 1940s. Texas was next-fastest growing, followed by Utah, Alaska, Colorado, and North Dakota.

States that prospered during the real-estate boom, such as Arizona, Nevada, and Florida, were already beginning to show a drop in growth when their populations were officially counted a year ago. Since then, the slowdown has spread to other burgeoning areas whose populations had previously withstood much of the dampening effects of the sluggish economy.

They include Georgia, South Carolina, Utah, and Idaho, whose annual growth over the last two years is now weaker than any time in the last decade.

Texas, the big 2010 winner owing to a diversified economy that attracted new residents during the recession, is seeing its growth slow as fewer people move there. In contrast, Democratic-leaning states such as California and New York are losing fewer residents to other states than before.

"Record low migration has continued to put a damper on what looked to be a Sun Belt growth explosion just five years ago," said William H. Frey, a demographer at the Brookings Institution, who reviewed the numbers. "States that seemed immune from the housing bust are now experiencing declining population growth as employment opportunities in a variety of industries contract, and as mortgages seem nearly impossible to obtain."

The Census Bureau released state population estimates as of July 1, 2011. The data show annual changes through births, deaths, and domestic and foreign migration.

In all, 38 states showed lower growth in 2010 and 2011 than in either of the previous two years during the recession. Twenty-three of these states are in South and West region. Moreover, 28 states showed either slower in-migration or greater out-migration than in either of the first two years of the recession.