Another example of what could work, but which does not seem to get anyattention, is to open up more part-time jobs. With lifespansincreasing (including people maintaining their health into later years)there are many older people who would love to keep working - just not50 to 60 hours per week. These part-time working people would continueto pay taxes. We need to find ways to use the enormous experience ofthese elder citizens.
As already mentioned by Stuart Kermes, providing economic incentivesfor women in less-developed countries - teaching them a trade so theycan increase the economic conditions of their families, etc., hasproven effective in lowering birth rates.
Additionally, we need not to provide incentives in our (US) socialsupport systems (welfare, etc.) for people to have keep having morechildren. We should introduce dis-incentives for larger family sizes. Perhaps some education credits for couples (or single parents) belowthe poverty level who limit their families to one or two children.
We could use advertising to help as well, promoting a prevalence forsmaller family size. It is possible to make smaller families a moresocially responsible and acceptable norm.