The world's population should be at most 50 million.

[The Grand Nudger]

See anybody forcing this?

Voluntary, capice??

Sure, sure....we can already get voluntarily sterilized, though..and theres no clear reason why the state would have a compelling interest in incentivizing that.  

It is likely the poorest will take advantage of such a program - and I doubt any will have any regrets for doing so. 

It might even be a good idea to offer twice as much - as college tuition.

Two problems, already.  Firstly, people have trouble paying tuition already..finding and then awarding twice that amount to people for literally doing nothing seems like a poor return on our tax investment.  Secondly, an economic inducement in the face of poverty strays away from the fundamentally voluntary nature of the proposal. It becomes deeply coercive. The same simply cant be said for economic assistence to parents...as no amount of having children will lift one up and out of poverty. Our government isn't that generous, lol. Just as a sidebar, you from the US or elsewhere? I;ve heard other welfare systems described and I can see where people living under those might be coming from..though just changing their welfare system seems to be the less drastic solution.

Or do you think poor people WANT to have kids they can ill afford??

Many do, sure.  Like the option being open to you to be sterilized, we seek to preserve that option for them.  If either of the two of you need government assistance..it's the folks with kids.

I'm still stuck on solving what problems we have before we go floating around the idea of getting rid of all the poors. Things like climate change and resource consumption, for example, are not issues of poor people creating a shortfall. They're the ones suffering it, lol.