Total fertility rate (TFR) is the most commonly used metric which measures the average number of births per woman in a population. The global average fertility rate now is just below 2.5 children per woman. Over the last 50 years, the global fertility rate decreased as modern men and women are choosing to have fewer children. In the pre-modern era, the fertility rates of 4.5 to 7 children per woman are considered as high fertility rates and these were most common. This is a good fertility rate. This was true for the U.S, the UK, Russia, India and China and many other countries.