The African country of Niger currently has the highest fertility rate, at 6.9, which means on average, a woman in Niger will have seven children in her lifetime.

With the exception of Afghanistan (14th), all of the top 30 countries are found on the African continent. In fact, it’s estimated that Africa will add 2.5 billion new people by 2100, while most continents will actually flatline in terms of population growth.

At the bottom of the rankings, the country with the lowest fertility rate is South Korea, at 0.84.

Interestingly, many of the current most populous countries of the world—including China, India, and the U.S.—are all below replacement levels of fertility, with parts of Europe and North America having had persistently low fertility levels since the 1970s.

Eoin Treacy's view

I’m from a relatively large family. I had five siblings. I remember my mother saying “after the third, the older ones look after the younger ones” That confirms the existence of a child care efficiency ratio implied in larger families.

That’s lost when families are smaller and older generations are dispersed. In fact, the fewer children a family has the higher the cost because hopes for the future are poured into enhancing that child’s competitive edge. That can involve paying for tutors, sports, music, schools, better neighbourhoods etc.