Very tricky question with Population Growth.?

This has to do with how population is counted. First, no one talks about couples having kids because it make the count hard. Women have kids. If each woman has 2 kids, this makes up for men not having kids. It does not take into account, that some baby girls will die before growing up to be women. That is where the 2.1 comes in. The extra children make up for girls who die.