Washington State's Growth Management Act directs cities to accommodate growth in their populations through a Comprehensive Plan. The State forecasts population growth at the county level and representatives of the jurisdictions within each county allocate that growth among the cities and unincorporated area in each county based on past trends and policy goals. Seattle, like all cities in King County, used households in its Comprehensive Plan, rather than population, because between censuses counts of housing units are more reliable than estimates of population. Also, a city's land use regulations directly affect the number of housing units that can be built.
Seattle's steady household size defies long-term trend.
Seattle's Comprehensive Plan included the goal of accommodating 50,000 to 60,000 additional households between 1994 and 2014, or an increase of between 19 and 23 percent, over the 20-year period. This goal was based on the need to accommodate a growing population under the assumption that the city's average household size would continue its historical decline and drop to 2.03 by 2000. Graph 1 shows the decline in household size from 2.7 in 1960 to 2.1 in 1990. The 2000 census found that the average household size for the city had in fact declined only slightly over the decade (from 2.09 in 1990 to 2.08 in 2000). The larger than expected household size recorded in the 2000 census means that fewer housing units are needed than anticipated to accommodate a given level of population growth. Graph 1: Seattle's Average Household Size Shows Stability
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Housing growth matches population growth.
The number of housing units in Seattle increased about nine percent (21,492 units) during the 1990s to reach 270,524 units, according to Census 2000. Seattle's population also grew nine percent over the decade. In 1994, the State estimated Seattle had approximately 259,000 housing units making the growth from 1994 to 2000 (30 percent of the 20-year planning period) nearly 4.5 percent, or about one-fifth of Seattle's 20-year goal. Seattle's Comprehensive Plan did not assume that the growth in population or housing units would be distributed evenly over the 20 years. The forecasts in the Plan showed that growth in both the number of households and the size of the population would be relatively slow in the mid-1990s. The growth rates were then forecast to gradually increase until 2001.
The 2000 census indicated that the number of households in Seattle grew slightly more by 2000 than anticipated in the Comprehensive Plan. However, because the average household size did not decline as much as was expected, the city's population is higher than that anticipated by the Plan. According to Census 2000, Seattle's 2000 population was about 15,000 higher than the Comprehensive Plan indicated.
OTHER INFORMATION ON POPULATION TRENDS:
