Sub-replacement fertility

Sub-replacement fertility is when a country has a birth rate that is lower than what is needed for the population to stay the same size. This means over time, the population will get smaller and smaller because not enough people are being born to replace the people who are dying. In some countries, even if everybody lives to a very old age, there are not enough newborns to keep the population stable. As a result, this can put a lot of pressure on their economy, health care system, and social services.