Many environmentalists and ecologists believe that world consumption has already exceeded the amount our planet can naturally replenish (in 1990). At that time, the global ecological footprint, a measure of that consumption, was growing at an annual rate of about 1.5 percent; by now it has nearly doubled that rate.
Based on my projections of the footprint’s growth, the world’s population will peak when GWP per unit of IP index (average of normalized life expectancy and happiness, multiplied by normalized population) is 174 percent of its 1990 value. At that time, in 2020, footprint per IP will be 155 percent of its 1990 value. That is, the economic cost of our existence will be three-fourths more, and the ecological cost of our existence will be one-half more. We will also have just doubled the total amount of resources we were using in 1990.
After the population peaks, more people will die than are born. Over the following 20 years the costs of survival will spike to over triple their 1990 values. Within 30 years of the peak most if not all of the population will be dead.
If we buy time by conserving as I suggested earlier (reducing consumption by one percent per decade saved, maintained over the number of decades to be saved), the economic cost will rise even as the ecological cost drops. As with business as usual, when the additional economic cost (since 1990) exceeds three-fourths what it was then, the population will reach a maximum. The decline of population will however take much longer.