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![]() ![]() The year of six billion Math of population Problematic projections Unsatisfied demand Was Malthus right? ![]() ![]() |
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Produce. Reproduce
If you were as simple-minded as we Why Filers, you'd figure that was it. But statisticians don't like to add --- they greatly prefer sophisticated math, and rely on percentages rather than absolute numbers to express population growth.
Conclusion? The math gets kinda complicated kinda fast, professor. We'll spare you the gruesome details, but just remember that the rate of increase depends on the number of children per woman, and on the length of generations -- her age at the first baby.
Thus, says Donald Waller, a University of Wisconsin-Madison professor of biology and ecology, if all women had three kids with a 15-year average generation time, the rate of population growth would be 2.7 percent. If the average spacing were 30 years, the growth would drop in half -- to 1.35 percent.
Waller notes that exponential growth (compound interest to economists) is characteristic of living organisms. One bacterium divides into two, which make four, then 8, 16, and pretty soon you have a whole lakeful of bacteria.
Doubling time
How do these factors translate into population predictions?
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