EXISTENCE OF EQUILIBRIA IN EXHAUSTIBLE RESOURCE INDUSTRIES NONCONVEXITIES AND DISCRETE VS CONTINUOUS-TIME

I demonstrate in a very general model that decreasing or U-shaped aver age cost curves always rule out competitive equilibrium in continuous- time models of extractive industries. Discrete-time models of these in dustries, however, can have competitive equilibria. Existence of compe titive equilibria in the presence of nonconvexities is sometimes more and sometimes less problematic for extractive industries than for indu stries making a producible commodity.