I refined my population-consumption model once again, after encountering some difficulties with applying it to other kinds of consumption, namely energy and gross domestic product. This time I took into account that population, like per capita consumption, is a power function rather than an exponential one (proportional to the year raised to a constant exponent). The dependence of population on resources that was my key insight in creating the model was accommodated by calculating the coefficient (proportionality “constant” of the power function) of population for a given year: Multiply the previous year’s coefficient by the ratio of resources at the beginning of that year to the resources at the beginning of the previous year. Unlike the last iteration of the model, I didn’t adjust the population for decreasing per capita consumption, since this was a guess that couldn’t be tested with existing data.
As before, the population based on the ecological footprint peaks by the middle of this century (8.2 billion people in 2038), but his time it effectively crashes, dropping below half its peak value in 2084 and finally reaching zero by 2444. In the model of world energy from 1980 to 2004, the population peaks higher and later (9.3 billion in 2053), and also crashes, falling below half the peak in 2105 and reaching zero by 2256 (significantly, this model accurately predicts known energy reserves). The model of Gross World Product (GWP, in fixed dollars) yields population projections higher than those for footprint and energy: Population peaks at 27.0 billion people in 2118, falls below half that amount by 2159, and drops to zero in 2406.
For all intents and purposes, the footprint and energy projections tell the same story. Around the middle of this century the world’s population will reach a maximum and then decline, falling to half the peak value around the end of the century. All of the projections show humanity being extinct within 440 years.