Suppose that all women in the world today began bearing children at replacement-level fertility rates of 2.1 children per woman. Explain why this would not immediately stop global population growth. About how long would it take for population growth to stabilize (assuming death rates did not rise)?

Answer 1

The effects of the birth rate per woman at a particular time are not felt until the females born then have lived out their child-bearing years. This would occur over about 20 to 40 years. The "birth rate per woman" can only be accurately established when the survey is done among women who have already completed child bearing. Women who are currently fertile must maintain the same birth rate until menopause before the full effects show up. This also takes an average of about 20 years.