probably favourite two-legger in general.
Fausty, is that you?
In short, I agree with the OP's goals, but not his way of getting there. I'm on my Ob-Gyn rotation in medical school right now, and it's a hard type of medicine to be involved in, since I strongly believe that most problems facing humanity right now come down to this planet having too many people.
I don't judge the 90% of women in labor whose charts list their job as 'unemployed' and their insurance as 'self-pay / charity care' -- many of these women are probably stay at home mothers with SOs who work. And even if not, poverty doesn't automatically make one an unfit parent. However, I very much do judge women who clearly don't want or can't handle more kids, but keep having more anyway.
I really think we should reach a point where all women in the world have one child, until the world population is down to 1~2 billion. However, I doubt very strongly that top-down government mandates are an effective way to achieve this. China only gets away with it because they are unabashedly undemocratic, and willing to tolerate some nasty side effects like forced sterilization and a lopsided gender ratio. Plus, the one child policy is largely flouted in rural areas of China, where more hands still make for easier farming, same as it ever was.
The places in the world that have organically, i.e. without a mandate, achieved a sub-replacement birthrate, have really two things in common:
1) Their agricultural sector does not rely on large amounts of human labor, and
2)
Their girls are well educated
No, it's not a direct correlation with wealth, as is often believed. There are some fairly rich countries that are fecund, and some fairly poor countries that aren't, because they meet the criteria above. You want to lower any population's birthrate? Raise female literacy to 100%, and encourage girls to pursue all the same educational and occupational opportunities as boys do. They'll have a lot more to do and think about besides being good (read: fecund) mothers and wives.
Also, encourage the natural trend toward movement of people from rural areas to cities, along with the mechanization of farming. Humanity's future is in cities, and let no tree hugging dirt worshiper tell you differently. Urban people have always had much fewer children than rural people -- there just isn't the space, nor for most people the finances or the need, for large broods.
I'd also be willing to try tax breaks and other positive incentives from the government to people who choose to have 1 or 0 children. If, for example, the US had an all-inclusive government provided health insurance plan available ONLY to families with one child, as well as fully subsidized contraception of a variety of types available to all, I bet you'd see the whole 'welfare mother' phenomenon disappear overnight. But notice these are carrots, not sticks.