Coordinated Population Forecast for Columbia County, its Urban Growth Boundaries (UGB), and Area Outside UGBs 2020-2070

Different areas within Oregon counties experience different growth patterns. Those patterns combine to collectively determine county‐level demographic changes. Columbia County is comprised of two types of areas: its urban‐growth boundary (UGB) areas (Clatskanie, Columbia City, Prescott, Rainier, Scappoose, St. Helens, and Vernonia) and areas outside those UGBs. Columbia County’s total population steadily increased in the 2000s, growing at 1.3 percent annually (see Figure 1). Some sub‐areas—such as Columbia City, Scappoose, and St. Helens along the Columbia River Highway—experienced faster population growth than the county, averaging between two and three percent growth annually. In contrast, Prescott and Vernonia lost population, and Clatskanie and Rainier grew less than one percent annually. The population growth that occurred in Columbia County between 2000 and 2010 resulted primarily from strong net in‐migration of adults older than 30 and their children. Though population growth due to natural increase (births minus deaths) was positive during the decade, it tended to represent a smaller proportion of total growth. By 2010, Columbia County’s natural increase began to dip, ultimately turning into natural decrease in 2018. This is due to several factors. Most notably, between 2000 and 2010, Columbia County’s total fertility rate fell over 50 percent faster than the statewide rate. The effects of this trend were compounded by net out‐migration of adults in their twenties, a migration pattern common in areas without a major university or city. These factors—combined with nationwide population aging—led to fewer births and more deaths each year and thus overall natural decrease