Population Growth: Components of Population Change
Population change occurs in two ways: natural increase (births minus deaths), and net migration (people moving in minus people moving out).
Every year since the state began registering vital events there have been more births than deaths, thus natural increase has been positive.
Net migration can be derived by subtracting natural increase from population change. There have been years in which Oregon had more out-migrants than in-migrants, most recently in the early to mid-1980s when Oregon suffered a recession longer and more severe than the national economic downturn. However, when generalized each decade between censuses, net migration has always been positive.
Natural increase peaked during the baby boom of the 1950s, when net migration was at its lowest level. In the current decade, an aging population and fertility rates below replacement level have resulted in the lowest level of natural increase since the 1930s.
The highest levels of net migration have been attained during periods of strong employment growth, including the 1940s war effort and in the 1970s and 1990s.