Equation 6 · Demography, Migration, and Urban Futures in Practice: An Advanced Technical Guide
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the age-and-sex-specific survival ratio for that interval. Read the equation part by part below; each part has a contextual explanation and a link to its mathematical background.
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where P is the population count, S is the age-and-sex-specific survival ratio for that interval, and M is net migration assigned to that cohort during the interval. The youngest cohort in each step is not aged forward from an existing cohort; it is generated fresh from the number of births, which is itself the product of age-specific fertility rates applied to the female population of childbearing age, by convention ages 15 to 49 [ 1 ] .
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