Population decrease will have the biggest impact.

Yeah and there's two ways to get there - planned and unplanned. It'll happen one way or the other.

Good news then: most of the world already has a decreasing population or about to start decreasing. Only exception being Africa.

Decades too late unless you suggest we start killing people.

Yes, but you cannot say that. We need more people, for money.

The unpopular answers are usually the correct ones.