Population Growth Curves

Some of the most interesting questions that arise in the context of intertemporal resource allocation concern the rate of utilization of those resources that are at the same time self-renewable and in principle exhaustible. Resources such as minerals and fossil fuels, with which we shall be much concerned in the forthcoming chapters, do not fall into this category, for they are not renewable. They are a prime example of exhaustible resources. The act of extracting and utilizing a unit of such a resource reduces the total stock by precisely that amount. There are no means by which the total stock can be increased. Improvement in technology (e.g. enabling one to mine deeper layers) can, of course, increase the quantity that can be extracted. But that is a different matter. Then again, discoveries of new deposits will increase the known available stock. But this too is a different matter.

Durable commodities like buildings and automobiles are also not in this category. Even if the entire stock of such a commodity were to be destroyed at a stroke, at least a part of the original stock could presumably be replaced in time. To the extent that such durables require exhaustible resources in their production, the possibilities of replenishing them will presumably be circumscribed by the availability of these exhaustible resources. But this again is a different matter.