Economies and Diseconomies of Scale

A firm's long run average cost curve usually looks like a U, and scale explains the shape. Early on, growing bigger lets a firm spread fixed costs, specialize workers into narrow tasks they get fast at, and buy inputs in bulk at discount prices. Output grows faster than inputs, so cost per unit falls. That's economies of scale, and it's why a bigger factory often beats a small one on price per item.

Keep growing, though, and a different force takes over. More workers and more plants mean more layers of management, slower communication, and harder coordination. Decisions that once took an afternoon now take a committee. Input costs may even creep up if the firm is so large it saturates its supply chain. Output growth starts lagging behind input growth, average cost turns upward, and that's diseconomies of scale. The point where the curve bottoms out, between the two, is minimum efficient scale: the smallest size at which a firm reaches the lowest average cost available to it.

This sits right behind the production function and right before market structure. Scale economies explain why some industries end up with a few huge firms (steel, cars) and others stay full of small ones (hair salons, bakeries): it depends on where minimum efficient scale falls relative to total market demand. In the perfect competition model coming next, firms are assumed small relative to the market, often because diseconomies of scale cap how big any one of them can profitably get.