20 billion is half again higher than the worst predictions for population growth. The world's population is expected to peak around 11B in 2100 or so, with outs

20 billion is half again higher than the worst predictions for population growth. The world's population is expected to peak around 11B in 2100 or so, with outside high predictions up to 14B. On what basis do you believe the population will hit 20B, especially with birth rates plummeting to near-replacement levels all around the world? What countries are going to go backwards, and why?