World Fertilty Rates by Country - Rise and Decline of Cultures

Why is fertility rate important?

Fertility rate is, basically, the number of children that the average woman will have in her lifetime.

If the average woman has exactly two children in her lifetime, this is just enough to replace herself and one man, and thus maintain the population.

Ultimately, this is the only thing that matters in determining long-term population growth. If the average woman has two children, then the number of people in the next generation will be the same as the number of people in this generation. You often hear people say that improved diet or medicene or other things that cause people to live longer cause population to grow, or that wars or other disasters cause population to shrink. But this is only true indirectly: only if it changes the number of children that the average woman has in her lifetime. That is, if many women die while still young, they may not live long enough to have all the children that they otherwise might have had. But beyond that, how long people live doesn't matter. Everybody still dies sooner or later. If a war wipes out a large number of people, this causes an immediate drop in the population, of course. For the time that the war lasts population growth becomes negative. But once the war is over, if the number of children per woman is the same, the old population growth rate will immediately resume. There is a temporary change in the total numbers, but the rate of growth does not change.