The Wong-Viner Envelope Theorem on the equality of long-run and short-run marginal costs (LRMC and SRMC) is reformulated for convex but generally nondifferentiable cost functions. The marginal cost can be formalized as the multi-valued subdifferential a.k.a. the subgradient set but, in itself,...

The “short-run approach” calculates long-run producer optima and general equilibria by building on short-run solutions to the producer’s profit maximization problem and on profit-based valuation of the fixed inputs. We outline this method and illustrate it on an example of peak-load pricing.