Washington’s population grew from 4.1 million in 1980 to 6.7 million in 2010 and is expected to reach 8.8 million by 2040.
Washington State Total Population
Source: Washington State Office of Financial Management
Source Data in Excel: http://www.ofm.wa.gov/pop/stfc/stfc2011/stfc_2011.xlsx
Washington State Annual Rate of Population Growth

For comparison, the U.S. annual population growth rate from 1980 to 2003 was 1.01% and is projected to continue that annual population growth rate through to 2030.
Washington State and U.S. Annual Rates of Population Growth

Historical Population and Growth Rates for the U.S. and Washington (1980 to 2009)

Projected Population and Growth Rates for the U.S. and Washington (2004 to 2030)

United States Projection = U.S. Census Bureau Projections 2004 to 2030
Washington State Projection = Washington State Office of Financial Management, (published November 2003)
NOTES:
-- Washington State data from Washington State Office of Financial Management, all other data sourced from the U.S. Census Bureau.
-- U.S. Census Year data is in bold above.
-- U.S. Census Bureau refers to estimates as population figures for all years present and past. Projections are for all future years.
-- The U.S. Census Bureau’s estimates for years 2000 to 2003 were updated and released December 18, 2003.
The U.S. Census Bureau’s projections for years 2004 to 2025 were last revised August 2, 2002.
As a result there is a lack of synchronization between the last estimate year (2003) and the
first projection year (2004). The published estimates appear in the tables below, but the graphs above
reflect a natural linear extrapolation from 2003 to 2004.
Source Web sites: U.S. Census Bureau and Washington State Office of Financial Management