While population growth statewide cooled to about 1.5 percent in 2007, the Tri-Cities continued to boom at two to three times the state average.

The state Office of Financial Management released numbers Wednesday showing population rankings for nearly 300 cities.

Despite growth of 5.3 percent for the 12 months ending April 1, 2008, Kennewick slipped from being the 12th-largest city to 14th.

Pasco, which had a 4.2 percent increase in population, gained a notch to become the 17th largest city in the Evergreen State.

Ken Nelson, Kennewick's director of economic growth, said rankings don't count as much as the real numbers that show the Tri-City area continues to attract people for jobs and quality of life.

"We don't care about the (population) rankings. What counts is the growth rate. (Businesses) like knowing that people keep coming here," he said.

Population in the Tri-Cities, which includes Kennewick, Pasco, Richland and West Richland, grew by 4 percent in the past year to 175,410, according to the state's estimates.

The four cities' combined population represents the fourth-largest municipal area, lagging only behind Seattle, Spokane and Tacoma.

Vancouver is the fourth-largest city by population, but has about 30,000 fewer residents than the four cities in the Tri-Cities area.

Kennewick is the largest municipality in the Tri-Cities with 65,860 residents, while Pasco is second with a population of 52,290.

Richland held onto its 20th ranking this year for population size among cities in Washington with 46,080 residents. And West Richland's population of 11,180 makes it 70th among the 291 cities that were included in the state's population ranking study.

Washington's top six cities by population have not changed positions since 2000. They continue to be Seattle (592,800), Spokane (204,400), Tacoma (202,700), Vancouver (162,400), Bellevue (119,200), and Everett (102,300).

Yakima, which had 84,300 in the recent population study, has been the 10th-largest city since 2003. It had growth of 1.6 percent for the year ending April 1.

Annexation-driven growth spurts in Renton and Auburn during 2007 pushed those communities' populations up several notches in the rankings.

Renton moved from 13th to 11th with a population gain of 31 percent that resulted in 78,780 residents. More than 16,000 residents joined the city in a 2,600-acre annexation.

Auburn's 67,005 population reflected a 33 percent population gain, which was the result of two annexations that lifted it from 17th to 13th ranking and passed Kennewick.

Dana Hinman, communications manager for the city of Auburn, said state and King County officials persuaded several westside cities, including Auburn, Renton and Federal Way, to annex large areas that were within those cities' growth management areas.

"The annexations were the result of the Growth Management Act. King County and the state made it possible to annex. We were encouraged to do this and we received incentive funds from the state and King County," Hinman said.

Voters in Auburn and Renton approved the annexations in elections last fall.

A statement from the Office of Financial Management noted a "moderate but continuing deceleration in state population growth since 2006, when annual state growth approached 120,000."

The latest numbers show total growth of 99,600 to bring the statewide population to an estimated 6.6 million.

In-migration due to people seeking or taking new jobs has dropped 27 percent in two years, said Theresa Lowe, the state's chief demographer.

Lowe said in a statement Wednesday that in-migration related to jobs went from 81,000 in 2006 to 70,000 in 2007, to 59,000 for 2008.

State officials said changes in school enrollment, housing, voters and driver's license registrations are indicator data they use to help estimate populations for the state's cities.

Officials also discovered that California and Oregon, which historically have been major sources for much of Washington's in-migration, aren't providing as many newcomers. Officials speculated the depressed housing market in those states has made it more difficult for people to sell and move.