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Oregon -- Population -- Statistics, Demographic surveys -- Oregon, Population forecasting -- Oregon -- Washington County


Different areas within Oregon counties experience different growth patterns. Those patterns combine to collectively determine county‐level demographic changes. Washington County is comprised of three types of areas: areas within Metro’s jurisdiction, urban‐growth boundary (UGB) areas outside of Metro’s jurisdiction (Banks, Gaston, and North Plains), and areas outside of Metro and those UGBs. In this report, we focus on Washington County as a whole as well as non‐Metro sub‐areas.

Washington County’s total population has grown swiftly over the last half century, only slowing modestly during Oregon’s deep 1980s recession. Since 1990, average annual growth rates have slowed from above 3 percent to around 1.5 percent during the 2010s (see Figure 3). Most of this population growth occurred within areas now part of Metro’s jurisdiction. Washington County’s small sub‐areas outside of Metro, on the other hand, exhibited a variety of growth patterns over the last two decades. After a housing boom in the late 1990s, population growth slowed in Banks. Nearby Gaston experienced limited growth, if any. And North Plains, the subarea closest to Washington County’s job centers, experienced steady growth since 2000, culminating in an ongoing surge in housing construction set to produce strong population gains in the 2020s.

Considered as a whole, Washington County’s population growth between 2000 and 2010 resulted from a healthy mix of natural population increase (births exceeding deaths) and consistent net in‐migration. Washington County especially excelled at attracting in‐migrants between 25 and 39, some with children in tow. Since 2009, Washington County’s natural increase has begun to decline in magnitude, falling from roughly 5,000 to 3,000 people annually. This is due to several factors. Most notably, between 2000 and 2010, Washington County’s total fertility rate fell twice as fast than the statewide rate—though from a higher starting point. This—combined with the national trend of aging population—led to fewer births and more deaths over time, and thus, declining natural increase.


This report is published by the Population Research Center at Portland State University, and is a product of the Oregon Population Forecast Program.

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