Excess Capacity and Allocative Inefficiency

Think about why every restaurant in town has a few empty tables on a normal Tuesday. Each restaurant sells a slightly different product: different menu, different atmosphere, different location. That differentiation gives each one a downward-sloping demand curve, like a mini monopoly. In the long run, entry and exit push economic profit to zero, which means the demand curve just touches, or is tangent to, the average total cost curve. But a downward-sloping demand curve can only be tangent to a U-shaped ATC curve on the falling part of ATC, left of its minimum. That leftward point is the firm's long-run output, and the gap between that output and the output at minimum ATC is excess capacity.

This tangency creates two separate efficiency failures, both visible on one graph. First, producing left of minimum ATC means the firm is not making the product at the lowest possible cost per unit; this is productive inefficiency. Second, because the firm faces a downward-sloping demand curve, marginal revenue sits below price, so the firm sets marginal revenue equal to marginal cost at an output where price still exceeds marginal cost; this is allocative inefficiency, since the price consumers pay overstates the marginal cost of producing one more unit. Both failures sit side by side at the same equilibrium point, below and left of where a competitive firm would land.

None of this means the restaurant is mismanaged. The firm is maximizing profit given the demand it faces; the inefficiency comes from market structure, not sloppy operation. The payoff for consumers is variety: more restaurants, more menus, more styles, each with some brand loyalty. That variety is worth something, and it is the reason this unit treats monopolistic competition as a real tradeoff rather than a simple failure compared to perfect competition.