What is meant by "population momentum"?

"Population momentum" refers to the phenomenon where a population continues to grow even after birth rates have declined. This occurs because there is a significant proportion of the population that falls within the reproductive age group.

When a society experiences high birth rates, a large number of individuals enter their childbearing years. Even if the birth rate subsequently drops, the existing young population continues to have children, resulting in sustained population growth. This means that a population can keep increasing for several decades even after the introduction of family planning measures or changes in social norms that lead to lower fertility rates.

This concept is essential for understanding demographic trends, as it highlights that reductions in fertility do not lead to immediate population stabilization. Instead, the effects of past high birth rates can lead to a "momentum" of growth that influences population size for years to come.