Quote by Wikipedia: Population Momentum

“Population momentum is a consequence of the demographic transition. Population momentum explains why a population will continue to grow even if the fertility rate declines. Population momentum occurs because it is not only the number of children per woman that determine population growth, but also the number of women in reproductive age. Eventually, when the fertility rate reaches the replacement rate and the population size of women in the reproductive age bracket stabilizes, the population achieves equilibrium and population momentum comes to an end. Population momentum has implications for population policy for a number of reasons. 1. With respect to high-fertility countries (for example in the developing world), a positive population momentum, meaning that the population is increasing, states that these countries will continue to grow despite large and rapid declines in fertility. 2. With respect to lowest-low fertility countries (for example in Europe), a negative population momentum implies that these countries may experience population decline even if they try to increase their rate of fertility to the replacement rate of 2.1. For example, some Eastern European countries show a population shrinkage even if their birth rates recovered to replacement level. Population momentum can become negative if the fertility rate is under replacement level for a long period of time.”

Quote by Wikipedia: Population Momentum