Energy to build it, energy to maintain it.

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8. To do this, you need to get people to stop having kids

Even China's 1 child policy hasn't worked. There are 400 million more Chinese now than when it was implemented in 1979. I was in Kuala Lumpur and Manila recently and every woman of birthing age seemed to have 3 or 4 kids trailing them. Religion is a major reason (one country is predominantly Muslim and the other is predominantly Catholic). India is even worse with their population expected to pass China's by 2025. Without a social safety net, people hope at least one of their brood will be successful enough to look after them in their old age and so keep having children and the cycle repeats generation after generation.