In nearly all developed countries, the birthrate is below the replacement level (2.1 children per woman). Countries like Italy, Japan and Russia are losing numbers and will be for the foreseeable future. The United States is the exception, but that for the most part is due to higher birthrates among Hispanics, both immigrants and native-born (check the latest Census figures). Birthrates in Mexico, however, have plummeted in recent years. There is an interesting dynamic going there, one I do not fully understand.

'Overpopulation' is a problem that will take care of itself with economics development, education, rights for women, etc. No reason for a Leviathan state, global one-child policies, or any other such nonsense.