On stockpiling natural resources

Persistent and significant privately held stockpiles of minerals have long been an important empirical regularity in the United States. Such stockpiles would not rationally be held in a traditional Hotelling-style model, though firms could be willing to hold inventories if extraction costs are stock-dependent. More plausibly, if prices are stochastic, and sufficiently volatile, firms have an incentive to hold inventories to smooth production over time.