In the early 1970s Ehrlich and Holdren devised a simple equation in dialogue with Commoner identifying three factors that created environmental impact. Thus, impact (I) was expressed as the product of (1) population, (P); (2) affluence (A); and (3) technology, (T):
I = P * A * T
Population is the number of people on the planet, affluence is measured in GDP per capita, and technology is environmental impact per GDP. When looking at the growth rates of each I, P, A, and T the formula changes towards this form:
dI = dP + dA + dT
In order to see how the impact changes from one year to the next one, you just have to sum up the changes in population increase, affluence, and technological progress.… Read more