It takes 2.1 children per woman to keep the population the same as it is today in the USA. In In some countries it takes over 3.0 because so more children die
before reaching their childbearing ages. Population numbers have been on the increase but not like they once were. In China they have a "one child" policy, the fertility rate in China has fallen from over 5.0 to 1.7 births per woman. I'm not sure what the answer would be but disease, murder and other unfortunate circumstances seems to keep the population numbers in check.
