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NPG Forum Ser. 1989 Dec:1-4.

How to get there from here: the demographic route to optimal population size.



Most Americans have a "built-in bias" towards growth. 25 years ago, Americans were concerned with too much growth. Zero population growth was accepted as a goal. The American perception has turned around in the last quarter century. From 1957, with a peak of 3.7, US fertility fell below the level needed to replace the population and reached 1.8 in 1972. Not all growth is good. 3 demographic variables account for all population size changes. In any young population, there is a growth momentum that is "built-in." In talking about the next 60-90 years demographic mathematical models show what would happen under constant conditions. The best known is the stable model. A stable condition comes about if age-specific birth and death rates remain constant over a long period of time. A stable population shows a constant growth rate. "No growth" is described as "stationarity." In 1982, migration was included in the open, stable model. There is a momentum for growth in the US population. It is assumed life expectancy will increase in future years. Fertility and immigration should be balanced. There is not much that can be done about fertility. Much, however, can be done to immigration. A maximum population of 300 million with decline starting before 2080 is practical. Lowering fertility to 1.5 live births per women is possible. Not too many Americans want to entirely end immigration. There are problems with advocating that zero population growth be at current levels, or lower. Some increases will happen because of the build-in growth momentum.

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