To maintain constant per capita consumption as a means of minimizing future population loss, we must be careful not to limit everyone to what they are consuming now. Note that “per capita consumption” is an average; there are great differences between countries and individuals. For countries, averages per citizen range between .04 and 5.0 times the world average (the former for the United Arab Emirates and the latter for Afghanistan).
One potential solution involves the public ownership of resources, where the total resources that people can use are limited based on population size. The internal distribution of those resources could then be managed by something like free market economics (with the illusion of private ownership).
Increasing the renewable resource base (capacity), another critical condition for long-term survival, would need to be encouraged without resulting in an overall increase in per capita consumption. This could be done in at least one of two ways: by economically treating capacity creation as a service worthy of higher income (enabling more consumption relative to other people); or allowing capacity creators’ offspring access to more of the additional capacity.
If humanity had not exceeded the world’s capacity with exponentially growing consumption, there would be no need for a distinction between “usable resources” and “total resources”; people could simply use whatever they could get. Unfortunately, the laws of physics do not permit unlimited exponential growth in the amount of usable resources; and people tend to move elsewhere or kill each other (if they can’t move) when they are forced to reduce what they consume.