I completely agree with what people are saying here. There needs to be a child cap. One per couple. And it needs to be strictly enforced, at least for 10 years or so. In Larry Niven's Ringworld, people were implanted with a small device that releases chemicals that make it impossible to reproduce. When a couple wants to have a SINGLE child, they could have the device removed. It works, and it's fair. If people weren't having enough children then regulations could permit more pregnancies.
We could have programs like this, make them voluntary at first. Then once people warm up to the idea, require it.
Destal said:
The birth rate has always been significantly lower for wealthier countries than it has been for second and third world countries. Plus, China tried this once.
I guess they just weren't trying hard enough. Besides, you could have as many kids as you want, but you only receive benefits for your first, under the Chinese system.
Going to other planets won't solve the problem. We simply do not (and will not) have the technology to travel safely to other worlds (at least for a few hundred years). Space Travel is notorious for running into fatal screw ups. Is packing tens of millions of people into tin cans (a project that would probably end up bankrupting every nation on Earth) and sending them off in ships that are extremely likely to fall apart long before they ever reach their destination really the best idea? If we had a way of traveling instantly from the surface of the Earth to an alien plant far away from here, sure go for it. Right now though, we don't have the science nor the technology nor even the funding to do it, and do it safely.
Right now, we need real world solutions.