The basic cohort component model has been well known for at least 100 years. Changes to the behavior of cohorts is hard to predict over generations, but usuall

The basic cohort component model has been well known for at least 100 years. Changes to the behavior of cohorts is hard to predict over generations, but usually somewhat mean reverting despite the exponential nature of the process. Predicting a future population of 400m is every bit as unrealistic as 4b.