But nearly everywhere else, the era of high fertility is ending. As women have gained more access to education and contraception, fewer babies are being born. Even in countries long associated with rapid growth, such as India and Mexico, birth rates are falling toward, or are already below, the replacement rate of 2.1 children per family. (Replacement rate is the number of kids each family needs to have to keep the country’s population the same over time.)
The change may take decades, but once it starts, the decline in population will likely accelerate. With fewer births, fewer girls grow up to have children, and if they have smaller families than their parents did, the cycle speeds up.
Some countries, like the United States, Australia, and Canada, where birth rates hover between 1.5 and 2, have blunted the impact of lower birth rates by encouraging immigrants to come and settle. But in Eastern Europe and parts of Asia, populations are already declining.