coercion

Governments should use whatever coercive power they have to force couples to have no more than two children, or one child for a single woman.

The military, for example, could mandate such requirements. The military is not a democracy; it's a top-down, hierarchical organization. You either obey orders, or you're out.

If we ever go to some type of universal basic income, limiting reproduction should also be part of the deal. If you want the income, you limit your childbearing. Even now, people who are either on welfare or dependent on the taxpayer in other ways for their sustenance should be forced to limit their reproduction in exchange for these handouts. I don't use the term handout derogatorily. I don't think we can let people starve or freeze, but they have responsibilities as well, and limiting their reproduction would be chief among them.