Page "Zero population growth" Paragraph 5

In the long term, zero population growth can be achieved when the birth rate of a population equals the death rate, i. e. replacement level is met and rate is stable.

Unstable rates can lead to drastic changes in population levels.

( This ignores migration, which is valid for the planet as whole, but not necessarily for a nation.

) A population that has been growing in the past will have a higher proportion of young people.

As it is younger people who have children, there is large time lag between the point at which the birth rate falls below the death rate and the point at which the population stops rising.