If the world’s population stabilizes at a constant value when the amount of available resources ceases to change (all consumed resources are renewable), my theoretical model of population and consumption projects that by 2278 the world’s population will be only twice the present population of the United States, and the per capita consumption will be practically equal to that of the United States today. Ideality (quality of life) would grow from 65 to 78. The world’s present population could live on 1/3 of its current per capita consumption (1/11 of that of the U.S.) if we reduced consumption immediately; and ideality would drop to 54. In both of these cases, business as usual and sustainability, the population would not crash, but we would be making a tradeoff between quantity and quality of life.
We could postpone the population decline by increasing our total available resources expanding into space until we reached the maximum speed attainable, but we would risk true population crash as per capita consumption was inevitably forced below what people needed for survival. If our per capita consumption continued rising at its current rate, and if we could travel at the speed of light (a physical impossibility), the population would crash in little more than about 3,000 years.