Loudoun County is less ethnically diverse than most of its Northern Virginia neighbors, but its population boom, one of the fastest in the country, is changing that quickly, according to new figures released by the U.S. Census Bureau.

Although the county has a higher percentage of non-Hispanic whites than the city of Alexandria, and Arlington, Fairfax and Prince William counties have, its minority population jumped from 20.3 percent in 2000 to 28 percent in 2004, marking one of the swiftest percentage increases in the country, according to a Brookings Institution analysis of new census estimates.

The census estimates illustrate a phenomenon that has been a central part of Loudoun's transformation from one of Virginia's most important agricultural centers to one of the nation's hottest housing markets.

Loudoun's Asian population, for instance, soared more than 150 percent from 2000 to 2004, to 23,542 residents, according to the census estimates. The black population grew 46 percent, to 17,586 residents. Residents of Hispanic or Latino heritage increased more than 100 percent, to 20,821. (People of any race can be of Hispanic ethnicity.)

The county's white population increased 32 percent during the period covered by the estimates, to 191,252. Overall, the county's population grew 41 percent, to 239,156.

Asians accounted for 5.5 percent of Loudoun's population in 2000 and 9.8 percent in 2004, according to the census figures. Hispanics or Latinos made up 5.9 percent of the population in 2000 and 8.7 percent in 2004. The percentage of blacks in Loudoun increased modestly, from 7.1 percent in 2000 to 7.4 percent in 2004.

While Loudoun and other outer counties became more diverse, the District and the close-in Virginia suburbs of Arlington and Alexandria gained more white residents. Demographers said high housing prices and the attraction of living closer to the region's urban core are helping shape housing choices.

The Washington region, with 5.9 million people, is 56 percent non-Hispanic white, 25 percent black, 10 percent Hispanic and 8 percent Asian, according to the estimates.