Minimum efficient scale

Minimum efficient scale (MES) is a term used in industrial organization to denote the smallest output that a plant (or firm) can produce such that its long run average costs are minimized. This concept is useful in determining the likely market structure of a market. For instance, if the minimum efficient scale is small relative to the overall size of the market (demand for the good), there will be a large number of firms. The firms in this market will be likely to behave in a perfectly competitive manor due to the large number of competitors.