WASHINGTON - The nation's great migration south and west is slowing, thanks to a housing crisis that is making it hard for many to move.

Most Southern and Western states are not growing nearly as fast as they were at the start of the decade, pausing a long-term trend fueled by the desire for open spaces and warmer climates, population estimates released yesterday by the U.S. Census Bureau show.

The development could affect the political map when U.S. House seats are divvied up after the 2010 census. Southern and Western states will still take seats away from those in the Northeast and Midwest - Florida could gain one or two House seats and Texas could pick up four.

But some seats hanging in the balance could stay put, and California could be in danger of losing a seat for the first time since statehood.

"People want to go to where it's warm and where there are a lot of amenities," said William Frey, a demographer at the Brookings Institution. "That's a long-term trend in this country."

"But people have stopped moving," he said. "It's a big risk when you move to a new place."

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

Utah was the fastest-growing state; its population climbed 2.5 percent from July 2007 to July 2008. It was followed by Arizona, Texas, North Carolina and Colorado.

Nevada was ranked eighth, after 23 years of ranking in the top four each year. It was listed as the fastest-growing state a year ago when the 2007 estimates were released. But adjustments to the numbers show that Utah was the fastest-growing in 2007 and Nevada was fourth.

Only Michigan and Rhode Island lost population from 2007 to 2008, the new estimates show. But growth rates fell in many states, even for those that had been adding residents at a rapid clip.

Pennsylvania's population grew 0.2 percent, to 12.45 million, and New Jersey's grew 0.3 percent, to 8.68 million.

Foreign immigration has slowed since the start of the decade, and fewer people are moving domestically. A study by the Pew Research Center found that only 13 percent of U.S. residents moved from 2006 to 2007 - the smallest percentage since the government began tracking movers in the late 1940s.

Florida has attracted more people from other states than any other state since the decade began. But from 2007 to 2008, more Floridians left than moved in - a net loss of nearly 9,300 people. The state still gained population from births and foreign immigration, but growth was slower than in earlier years.

From 2007 to 2008, California had the biggest net loss of people moving to other states - more than 144,000. It was followed by New York, Michigan, New Jersey and Illinois.

Attracting the most people from other states during the period were Texas, North Carolina, Arizona, Georgia and South Carolina.

The population shifts will be felt after the 2010 census, when the nation apportions the 435 U.S. House seats, based on population. Texas stands to be the biggest winner, while Ohio might lose two seats, according to projections by Kim Brace of Election Data Services, a Virginia-based firm that crunches political numbers.

New Jersey and Pennsylvania are also projected to lose single seats, as are Illinois, Iowa, Louisiana, Massachusetts, Michigan, Minnesota, Missouri and New York.