It shows that efficient exploitation of a nonrenewable and nonaugmentable resource would, under otherwise stable economic conditions, lead to a depletion of the resource. The rule states that this would lead to a net price or "Hotelling rent" for it that rose annually at a rate equal to the rate of interest, reflecting the increasing scarcity of the resource. Nonaugmentable resources of inorganic materials (i.e. minerals) are uncommon; most resources can be augmented by recycling and by the existence and use of substitutes for the end-use products (see below).