One fundamental decision will govern the future of humanity. We can either choose to live within our available resources, or we can try to increase the amount of resources.
To live within our available resources, we will need to do two things simultaneously: Stop population growth, and decrease our per capita consumption at a rate no less than 0.5 percent per year to 20 percent of its current value (by 2331). The population would level off without falling, and ideality would level off at 50 percent. If we could continue growing capacity (renewable resources) by 0.5 percent per year to a maximum of six billion hectares, then the target per capita consumption would be 30 percent of the current amount, reached by 2304.
If we choose to grow our resources, to maximize population as long as possible we will need to maintain a resource growth rate of at least 5.1 percent. Assume that by 2385 we can reach resources at the speed of an Apollo spacecraft on its way to the Moon and one global hectare of consumption is equivalent to a mass of 330 pounds; then our population could grow to a maximum of 21 trillion by 2440 and then plummet to zero by 2478. We could last until at least 2663 with a population of about three quadrillion people if we focused on consuming the entire mass of the Earth, but we would need to consume the entire Solar System’s (non-stellar) mass by 2855 to continue, which would require our consumption radius to be increasing at several thousand times lunar flight speed.
The sum of the Ideal World Index from 2000, to one significant digit, is 400 for business as usual; at least 3,000 for constant population; and 300,000 for growing resources (60 million if we consume the Earth and 3 billion if we consume the Solar System while continuing to increase resources).