"Louisiana lost the most population from 2005 to 2006. It lost almost 220,000 people over that time, or almost 5 percent of its population," Harper said, and it's no surprise why.
"Look at its internal migration from 2005 to 2006, and we see a negative 241,000, so I think it's pretty clear that most of that is due to (Hurricane) Katrina," he said.
"All of the ten fastest-growing states were either in the South or the West," Harper said. "North Carolina replaced New Jersey as the nation's tenth most populous state, and Texas did have a very large numeric increase from 2005 to 2006. It added almost 580,000 people."
Arizona led the nation with a population growth rate of 3.6 percent in the past year, followed by Nevada, Idaho, Georgia and Texas.
"There are housing developments sprouting everywhere, whether they are on former farmland or in the desert," said Tom Rex, associate director of the Center for Competitiveness and Prosperity Research at Arizona State University.
The pace of development has strained Arizona's resources and preoccupied local officials, Rex said.
"All they can think about is getting the sewer lines out to the new housing and getting the roads in," he said.
"Arizona has been gaining population through all of the components: strong migration from other states, as well as international migration, and natural increase, which is just births minus deaths," Harper said.
Arizona added about 32,000 immigrants in the past year. It added four times that many people who were relocating from other states. The biggest donor state: California.
"It used to be merely a retirement magnet for Midwest seniors," said William Frey, a demographer at the Brookings Institution, a Washington think tank. "Now it's also a front door for immigrants from Mexico and an escape hatch for Californians seeking affordable housing."
The Census Bureau estimates annual state population totals using local records of births and deaths, IRS records of people moving within the United States and census statistics on immigrants. The bureau does not distinguish between legal and illegal immigrants, and most experts believe that the number of illegal immigrants is underestimated.
Among other findings for 2006:
- Texas was followed by Florida, California, Georgia and Arizona in gaining the most people.
- Four states and the District of Columbia lost population: Louisiana, New York, Rhode Island and Michigan.
The South had a net gain of a half million people relocating there from other parts of the U.S., while the Northeast had a net loss of 375,000 people and the Midwest lost 184,000, according to the census estimates.
The West added 53,000 people from other parts of the U.S., even though California lost nearly 300,000 people to other states.
Texas passed Florida as the top destination, in part from people fleeing the aftermath of Hurricane Katrina.
Other relatively affordable southern states such as Georgia, North Carolina, South Carolina and Tennessee also had significant increases in people moving there from other states.
"Good climate and affordability seem to be the draws for Americans this decade," Frey said.
In the Northeast, New York, New Jersey and Massachusetts continued to lose large numbers of people to other states. In the Midwest, the big losers were Illinois, Michigan and Ohio.
Louisiana had been losing people to other states for years before Hurricane Katrina hit, though the storm exacerbated the problem, said Elliott Stonecipher, a veteran Louisiana demographer and pollster. Last year's loss amounted to nearly 5 percent of the state's people.
"The numbers make it clear that Katrina has had an incredibly negative effect," Stonecipher said. "But pre-Katrina, Louisiana was already in trouble."