The Seattle-Tacoma-Bellevue metropolitan area economy ranks as third strongest in the U.S., according to ratings by Policom Corp., an independent research firm.

Washington DC, anchored by an expanding federal government, retained its 2011 position atop the list, followed by Des Moines, Iowa, which is buoyed by a growing finance and insurance sector.

Policom creates the rankings using 23 different economic factors over a twenty year period. For the current rankings data covered the period 1992-2010. The highest ranked areas have had rapid, consistent growth in both size and quality for an extended period of time. The lowest ranked areas have been in volatile decline for an extended period of time.

Policom specializes in analyzing local and state economies. It annually ranks the 366 Metropolitan Statistical Areas and 576 Micropolitan Statistical Areas (smaller economies that do not have city with a population greater than 50,000 people).

Rounding out the top 10 list of metropolitan areas with the strongest economies are Nashville-Davidson-Murfreesboro-Franklin, Tenn., Austin-Round Rock-San Marcos, Tex., Salt Lake City, Madison, Wis., Kansas City, Mo.-Kan., Sioux Falls, SD, San Antonio-New Braunfels, Tex.

In addition to Seattle, ten metro areas in Washington were ranked, including:

Olympia (No. 11)
Kennewick-Pasco, Richland (13)
Portland-Vancouver-Hillsboro (51)
Bremerton-Silverdale (61)
Bellingham (65)
Mount Vernon-Anacortes (90)
Spokane (109)
Yakima (227)
Wenatchee-E. Wenatchee (259)
Longview (294)

Concord, the capital of New Hampshire, topped the list of 576 Micropolitan areas. Among micropolitan areas within Washington, Ellensburg ranked highest at No. 37. Other areas on the list and their rankings included:

Walla Walla (54)
Moses Lake (100)
Oak Harbor (125)
Shelton (128)
Port Angeles (148)
Pullman (266))
Centralia (294)
Aberdeen (318)

From its research, Policom determines if an area is growing or declining, what is causing this to happen, and offers ideas and solutions to communities to improve the situation.

"The rankings do not reflect the latest ‘hotspot’ or boom town, but the areas which have the best economic foundation," explained William H. Fruth, president of Policom. "While most communities have slowed or declined during this recession, the strongest areas have been able to weather the storm," he noted.