I think child mortality is counted as deaths before age five; I think it's lower if you count survival to adulthood and then having children. For population to

I think child mortality is counted as deaths before age five; I think it's lower if you count survival to adulthood and then having children. For population to remain constant each couple has to have two children survive to that point (on average; if some people have larger families and some have none it would balance out). Regardless, having half your children die as the norm is a pretty unpleasant reality.