I=PAT is
the size of the population (P) is multiplied by the average affluence or consumption per individual (A), and that in turn is multiplied by some measure of the technology (T) that services and drives the consumption. Thus commuting in automobiles powered by subsidized fossil fuels on proliferating freeways creates a much greater T factor than commuting on bikes using simple paths or working at home on a computer network. The product of P, A, and T is Impact (I), a rough estimate of how much humanity is degrading the ecosystem services it depends upon.
This is a very well written and extremely thought provoking article on overpopulation and overconsumption. It is worth your time to read.
How old is this post? I don’t see a date on the blog.
However, I would encourage you to think on something other than P as an important variable. I don’t see a marker for GDP which is a way of measuring the economy. And I would say that the economy is a key factor as cars, factories, electronics, and power plants are all part of it and sources or promoters of pollution (which would be I or impact).
Why the economy rather than the population, because humans themselves are eating coal and turning it to CO2 (and air-born mercury, among other things). Thus I’m encouraging you to look more at direct sources of pollution.