Hi,
Not really. You are overlooking the compounding of change. You are arguing on the basis of a linear model, but the better model is exponential.
For instance, if you assume a constant death rate of 0.85%/year and no births, then in 2110 the projected world population would be approximately 3 billion, the youngest of whom would be 100 years old. Not a realistic result. The problem is that both the death rate and the birth rate depend on not just the population size, but on the population distribution and sex.
A slightly better calculation gives a world population of 4.8 billion in 2050 if each woman has (on the average) only 1 child. An average of 0.6 would give a population of 4.2 billion.
There are actually some counter intuitive things going on here. For instance, the present death rate is artificially low because of the increase in life expectancy in third world countries.
However, I agree with your projections for India and Africa. Your prediction of an overshoot and decline seem most probable. Stabilization at the 8 billion, not so much. Once a "small family" culture has been adopted over most of the world, the next crisis will probably be human extinction. That's the problem with any rate other than zero -- it leads to explosion or extinction.
--Pete
(06-02-2011, 01:39 PM)Jester Wrote: Not impossible, but only in the case of a complete stop on all reproduction.
Not really. You are overlooking the compounding of change. You are arguing on the basis of a linear model, but the better model is exponential.
For instance, if you assume a constant death rate of 0.85%/year and no births, then in 2110 the projected world population would be approximately 3 billion, the youngest of whom would be 100 years old. Not a realistic result. The problem is that both the death rate and the birth rate depend on not just the population size, but on the population distribution and sex.
A slightly better calculation gives a world population of 4.8 billion in 2050 if each woman has (on the average) only 1 child. An average of 0.6 would give a population of 4.2 billion.
There are actually some counter intuitive things going on here. For instance, the present death rate is artificially low because of the increase in life expectancy in third world countries.
However, I agree with your projections for India and Africa. Your prediction of an overshoot and decline seem most probable. Stabilization at the 8 billion, not so much. Once a "small family" culture has been adopted over most of the world, the next crisis will probably be human extinction. That's the problem with any rate other than zero -- it leads to explosion or extinction.
--Pete
How big was the aquarium in Noah's ark?