What is the replacement rate for a population to maintain itself?

The replacement rate required for a population to maintain itself is typically 2.1 children per woman over her lifetime. This figure accounts for the need to replace the current population and includes a buffer for infant mortality and other factors that prevent all children from surviving to adulthood.

The standard replacement level is slightly above 2.0 because, while each woman needs to have two children to replace herself and her partner, the additional 0.1 accounts for demographic factors such as the sex ratio at birth and the mortality rates of children and adults. This means that a total fertility rate of 2.1 is necessary for a stable population without immigration.

The other numbers listed, like 1.5 and 2.0, do not account for these critical factors and would lead to a declining population over time if the fertility rate dipped to these levels consistently. A rate of 2.5, while still above the replacement level, exceeds what is needed to maintain population stability in the absence of significant mortality concerns.