Updated annually in November.

Small Area Estimates Program (SAEP) estimates are meant to provide a consistent set of small area population and housing data for statewide applications. SAEP estimates are generated for census areas and other areas of statewide significance.

Small area estimates program: GIS shapefiles for select census geographic areas and other areas of statewide significance. Includes annual population and housing estimates from 2010 onwards.

OFM produces annual population estimates for ‘special areas’ required by statue.  Special areas include highway urban areas, public transportation benefit areas, and the thermal electric generating facility area.  The special area estimates are based on data produced by the Small Area Estimate Program using GIS-based spatial interpolation procedures.

Updated annually in July

Population density is the average number of people per unit of land area. In the U.S., the most common unit of population density is persons per square mile. The land area measurement excludes lakes and other water areas within.

Population change

In accordance with RCW 43.62.035, the Office of Financial Management shall determine the percentage increase in population for each county over the preceding ten-year period, as of April 1.