Internal and external economies of scale, diseconomies of scale, the long-run average cost curve, minimum efficient scale, and the link to returns to scale.

What this dot point is asking

AQA wants you to explain internal and external economies of scale, diseconomies of scale, the shape of the long-run average cost (LRAC) curve, and the concept of minimum efficient scale (MES) and its link to returns to scale. This explains why some industries are dominated by a few large firms.

Internal economies of scale

The main types, often remembered with the mnemonic "TRAM-FP", are:

• Technical, from larger and more efficient capital and from the spreading of indivisible fixed costs (a blast furnace or a research lab).
• Risk-bearing, from diversifying across products and markets so that a downturn in one is offset by another.
• Marketing, from spreading advertising and a sales force over more units.
• Managerial, from employing specialist managers whose cost is spread thinly.
• Financial, from cheaper borrowing because large firms are lower-risk to lenders.
• Purchasing, from bulk-buying discounts when ordering inputs in large volumes.

External economies of scale

Examples include a local pool of skilled labour, specialist suppliers and infrastructure locating nearby, and shared training facilities. These are often seen in industrial clusters such as Silicon Valley for technology or the City of London for finance, where every firm benefits from the area's reputation and ecosystem.

Diseconomies of scale and the LRAC curve

This links to returns to scale: increasing returns (output rises proportionately more than inputs) drive falling LRAC, constant returns give a flat section, and decreasing returns drive rising LRAC. The MES is the lowest output at which the firm minimises long-run average cost. If MES is large relative to the market, only a few large firms can survive, which helps explain concentrated markets such as cars, steel and aircraft.

The long run versus the short run

It is essential to separate economies of scale from the short-run cost curves. In the short run at least one factor (usually capital) is fixed, and the U-shaped short-run average cost curve arises from the law of diminishing returns. In the long run all factors are variable, and the firm can move to a larger plant size. The long-run average cost curve is an envelope of many short-run average cost curves, each representing a different scale of operation. As the firm expands, it moves onto lower short-run curves while economies of scale dominate, then onto higher ones once diseconomies set in. Answers that treat economies of scale as a short-run idea, or that confuse diminishing returns with diseconomies of scale, lose marks.

Evaluation: are economies of scale always good?

Economies of scale lower unit costs, which can mean lower prices, higher profits to fund investment, and stronger international competitiveness. However, growth that pushes a firm past its MES into diseconomies raises costs, and a large MES relative to the market can entrench monopoly power and reduce competition and choice. The policy implication is nuanced: large scale can be efficient (a natural monopoly), but it may require regulation to ensure cost savings are passed to consumers rather than captured as supernormal profit.