Population Dynamics: Momentum of Population Growth

This article summarizes the recent literature on population momentum, usually defined as the subsequent population growth or decline after replacement conditions have been achieved. We review total momentum, its constituent parts (nonstable and stable momentum), trends over time, and how momentum is affected by immigration and emigration. Numerical examples are provided. The unifying concept is that momentum is created by a deviation between a population’s observed age distribution and its underlying stationary (or sometimes stable) age distribution, especially at younger ages.