The total fertility rate (TFR) is a key demographic indicator that represents the average number of children that would be born alive to a woman over her lifetime if she were to experience the exact current age-specific fertility rates (births per woman at each age) through all her childbearing years (typically considered to be from age 15 to 49), and if she were to survive from birth to the end of her reproductive life. It is a hypothetical measure that provides an estimate of the average family size in a population based on current trends in fertility. A TFR of around 2.1 children per woman is generally considered the replacement level, which is the average number of children needed to replace the parents and maintain a stable population size in the long run, assuming no migration. TFRs vary significantly across different countries and regions due to a variety of social, economic, cultural, and health-related factors.