How does human population achieve zero population growth? What would the birth rate need to be?

For the human population to achieve zero growth, the birth rate could be anything, but this rate needs to be balanced by the rate at which the area is losing people. Remember, when we discuss the growth rate, we're discussing the change in population.

For example, if ten babies are born in your town this year but ten people die, your total population actually remains the same. You've gained ten people but you also lost ten people. Your growth rate remains at zero.

If we take into consideration immigration and emigration, the idea remains the same. If you have a population of 500, and 15 people are added to your population over three years, but 5 people die and 10 people leave your population to join another one, the total population after three years remains at 500. Your growth rate remains at zero.

Zero population growth (ZPG) occurs when the number of births equals the number of deaths in a population over a certain period. To achieve ZPG, the birth rate would need to match the death rate. This would typically require a birth rate of around 2.1 children per woman, known as the replacement level fertility rate, accounting for mortality rates and gender imbalances. If the birth rate exceeds the replacement level fertility rate, population growth will occur, whereas if it falls below, the population will decline over time.