population momentum

Population momentum refers to the tendency of a highly fertile population to continue growing for decades, even after fertility rates decline. This occurs because a youthful age structure means there are many young people who will enter their reproductive years, leading to continued population increase. This phenomenon is significant for developing countries facing rapid growth and resource limitations.1

Unlike a sudden "population bomb," population growth is more like a slow-moving glacier, with long-lasting momentum. The basic components of population change are births and deaths in a closed system. In open populations, migration also plays a role. Population growth is the combination of natural increase (births minus deaths) and migration. Historically, population growth was slow due to high mortality rates, but it accelerated after 1750 with improvements in living standards and public health.123