World population growth history
Adding the next billion took just 123 years.
Adding the next billion took 33 years.
Adding the next billion took just 13 years--as did adding the each of the next 3 billions.
I'm not part of the school that believes governments should enact draconian population-control measures, but connnecting dots like this is pretty thought-provoking. Reason is that the big cities are cesspools of the worst of human behavior, and growth of those cities is almost certain to make that worse.
Doesn't bode well.