Total fertility rate worldwide 1950-2100
Today, globally, the average woman of childbearing is expected to give birth to approximately 2.3 children over the course of their lifetime. In pre-industrial times, the average woman could expect to have somewhere between five and ten children throughout their lifetime, however, the onset of the demographic transition then sees fertility rates fall significantly. Factors influencing this include the reduction in childhood mortality, where mothers do not feel the need to compensate for lost children, the increase in women's autonomy, and improved contraception access and efficacy.
Recent decades
Between the 1950s and 1970s, the global fertility rate was roughly five children per woman - this was partly due to the post-WWII baby boom in many countries, on top of already-high rates in less-developed countries. The drop around 1960 can be attributed to China's "Great Leap Forward", where famine and disease in the world's most populous country saw the global fertility rate drop by roughly 0.5 children per woman. Between the 1970s and today, fertility rates fell consistently, although the rate of decline noticeably slowed as the Baby Boomer generation then began having their own children.
Replacement level fertility
Replacement level fertility, i.e. the number of children born per woman that a population needs for long-term stability, is approximately 2.1 children per woman. Populations may continue to grow naturally despite below-replacement level fertility, due to reduced mortality and increased life expectancy, however, these will plateau with time and then population decline will occur. It is believed that the global fertility rate will drop below replacement level in the mid-2050s, although improvements in healthcare and living standards will see population growth continue into the 2080s, when the global population will then start falling.