Also called replacement level, replacement rate is the rate at which women must give births to maintain current population levels of a city, state, country or any particular region. In other words, it determines the total fertility rate required or the number of kids existing women (falling within childbearing years, i.e. 15-44 years) should give birth to for sustaining current population.
The rate takes into account the births needed to compensate for any loss of population due to death or other reasons. A higher mortality rate will increase a region’s replacement rate. Immigration, emigration, etc. also play a role in determining replacement rate.
Generally, replacement rate is lower in developed countries compared to developing regions because the need to keep up with fellow citizens is lesser in urbanized and developed areas. In other words, the population in developed countries is not expected to increase phenomenally. Lower replacement rates are observed in countries with a low total infertility rate or where the population is on the decline.