| Who are "they"? Hypotheses and projections are constantly refined. But in comparison to estimates on things like coal or climate, the population growth models are almost trivially simple, and while the numbers are adjusted up and down regularly to account for actual data, all data we have show the population growth consistently slowing down. For starters, one of the things that make the population models straightforward compared to a lot of other things we might try to model, is that we can compare countries, and as it happens there are patterns that have consistently applied to countries as they develop, and that we have detailed data on: As life expectancy increases, growth rates drop to near or below maintenance rates. Unless the remaining countries with rapid growth are somehow drastically different, it would take massive, earth-shattering changes for the population growth not to stop. It's not realistically a question of if it stops, but when and how high the peak will be, and how much the population will fall back afterwards before growth resumes (the expectation is that it will fall back because we get a "bulge" similar to what we're seeing these days due to the baby-boomer generation, and eventually the people in that bulge will start to die off). Even many developing countries have long ago entered into the phase where it is not birth rates that is the cause of ongoing growth, but improving life expectancy, which means that their growth will eventually stop. And with countries like China heading rapidly towards contraction as early as 2030 (with net growth now down to around 1/3 of its peak in the mid 80's, driven by a fertility rate far below maintenance), even the remaining high growth countries would have to dramaticall raise their population growth if we are to continue seeing overall growth. |