Business I / Population and Urbanization
Practice question · Multiple choice

A country's fertility rate falls below replacement today, and its population keeps growing for another thirty years. What explains the lag?

Hints
  1. Ask how many potential parents there are, not how many children each has.
  2. A rate is per person. What does the age structure contribute?
Show the answer

D. Population momentum, from a large cohort of childbearing age

Why

A rate below replacement multiplied by an unusually large parent cohort still yields more births than deaths, and the structure takes a generation to work through. This is why demographic forecasts are unusually reliable, the people who will be forty in forty years are already born.

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