The fertility rate required in a country to keep its population steady. In rich countries, this is usually reckoned to be 2. 1 children per woman, the extra 0. 1 reflecting the likelihood that some children will die before their parents. In poorer countries with higher infant mortality, the replacement rate may be much higher. In many countries, since the early 1990s the fertility rate has fallen below the replacement rate. There has been much debate about why, and much agreement that, if this trend continues, those countries may face long-term problems such as a relatively growing proportion of retired older people having to be supported by a relatively shrinking proportion of younger people.