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


Different parts of the county experience differing growth patterns. Local trends within the UGBs and the area outside them collectively influence population growth rates for the county as a whole.

Marion County’s total population has grown steadily since 2000, with an average annual growth rate of one percent between 2000 and 2010 (Figure 1). However, some of its sub-areas experienced more rapid population growth while others experienced opposite trends during the 2000s. Donald and Turner posted the highest average annual growth rates at 4.9 and 4.4 percent, respectively, during the 2000 to 2010 period. Concurrently, the Marion portions of Idanha and Lyons both experienced negative average annual growth rates at -6.3 and -6.2 percent, respectively.

Marion County’s positive population growth in the 2000s was largely the result of substantial net in-migration. Meanwhile, an aging population not only led to an increase in deaths but also resulted in a smaller proportion of women in their childbearing years. This, along with more women choosing to have fewer children and having them at older ages has led to fewer births in recent years. The larger number of births relative to deaths caused a natural increase (more births than deaths) in every year from 2000 to 2015. While natural increase outweighed net in-migration for the majority of the 2000s, net in-migration largely increased in 2014 and 2015 and, in the latter year, outpaced natural increase (Figure 12).

Total population in Marion County as a whole and in its sub-areas will likely grow at a slightly faster pace in the near-term (2017 to 2035) compared to the long-term (Figure 1). The tapering of growth rates is largely driven by an aging population—a demographic trend which is expected to contribute to a diminishing natural increase (more births than deaths). As natural increase lessens occurs, population growth will become increasingly reliant on net in-migration.

Even so, Marion County’s total population is forecast to increase by more than 67,000 over the next 18 years (2017-2035) and by more than 175,000 over the entire 50 year forecast period (2017-2067). Sub-areas that showed stronger population growth in the 2000s are generally expected to experience slower rates of population growth during the forecast period, while sub-areas that experienced negative growth rates are expected to experience very slight positive growth rates with the exception of Lyons.


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

The introductory presentation, preliminary forecast presentation, and Marion County final forecast tables are attached to this document as supplemental files.

Persistent Identifier

Marion intro presentation.pdf (3298 kB)
Introductory presentation

Marion_prelim_presentation.pdf (1559 kB)
Preliminary presentation

Marion_County_Final_Forecast_Tables.xlsx (135 kB)