Fundamentals of Business Economics and Management · Theory of Production
Economies and Diseconomies of Scale: Internal and External
Updated 10 October 2026 · Fact-checked
Economies of scale are cost advantages that cut average cost per unit as output grows. Internal economies come from a firm's own expansion. External economies come from growth of the whole industry. Diseconomies of scale are the opposite: past a point, growth pushes average cost up. Identify the source, then classify.
Understand Economies and Diseconomies of Scale
When a firm grows, its cost per unit does not always stay the same. Sometimes it falls. Sometimes, after a point, it rises. This change in average cost caused by a change in the scale of production is what this topic is about.
Economies of scale are the advantages that reduce average cost as output rises. Internal economies arise inside the firm because of its own size. They include technical economies (large machines, mass production), managerial economies (specialist managers), marketing economies (bulk advertising), financial economies (cheaper loans for a large firm), risk-bearing economies (many products and markets) and labour economies (division of labour).
External economies arise outside the firm, from growth of the industry or its location. All firms in the industry enjoy them. Examples: a skilled labour pool in a textile cluster like Tiruppur, better roads and power supply, supplier firms setting up nearby, and shared research or training institutes. Remember the test: if the benefit comes from the firm's own size, it is internal. If it comes from the industry's size, it is external.
Diseconomies of scale are the disadvantages that raise average cost when a firm or industry grows too large. Internal diseconomies include management problems (slow decisions, poor coordination), labour problems (low morale, strikes) and technical limits. External diseconomies include traffic jams, higher rents, higher wages and scarce raw materials when too many firms crowd one area.
On the long-run average cost curve, economies of scale make the curve slope down. Diseconomies make it slope up. Between them the curve is flat where costs stay constant.
Key formulas to remember
- Average cost
- AC = Total cost ÷ Output
- Economies of scale mean AC falls as output rises. Diseconomies mean AC rises.
- Internal vs external test
- Source of benefit: own size = internal; industry size = external
- Use this rule to classify any example in one step.
- Long-run AC curve shape
- Falling AC = economies; flat AC = constant; rising AC = diseconomies
- The curve is usually U-shaped (or saucer-shaped) in textbooks.
How to solve Economies and Diseconomies of Scale questions
Use this method for any question on economies or diseconomies of scale.
- 1Read the situation and ask what changed: the firm's output, or the industry's size.
- 2Ask whether average cost per unit is falling or rising.
- 3If cost falls, it is an economy. If cost rises, it is a diseconomy.
- 4Find the source. Own size or own decisions mean internal. Industry growth or location means external.
- 5Match the specific type: technical, managerial, marketing, financial, risk-bearing or labour for internal.
- 6Check each option against the exact definition and drop the ones with the wrong source or wrong direction.
- 7Pick the option that fits both direction and source.
Quickest way: Two-question filter
When to use it: Use this for MCQs that give an example and ask you to classify it.
- Question 1: Does cost per unit fall or rise? This gives economy or diseconomy.
- Question 2: Is the cause inside one firm or across the industry? This gives internal or external.
- Keywords: bulk buying, big machines, specialist managers, cheaper loans point to internal. Skilled labour pool, supplier cluster, better transport in the area point to external.
- Keywords: poor coordination, delays, red tape point to internal diseconomies. Congestion and rising rents point to external diseconomies.
Common mistakes in Economies and Diseconomies of Scale
Calling an industry-wide benefit an internal economy.
Students see a cost fall and stop there without checking who gets the benefit.
Fix: Ask who benefits. If every firm in the industry gains, it is external.
Confusing economies of scale with returns to scale.
Both deal with scale and look similar.
Fix: Returns to scale link inputs to physical output. Economies of scale link output to cost per unit.
Thinking diseconomies of scale mean total cost falls or that the firm makes a loss.
The word 'dis' is misread.
Fix: Diseconomies mean average cost per unit rises. Total cost still rises with output.
Treating all economies as only technical.
Textbook examples focus on machinery.
Fix: Learn all six internal types: technical, managerial, marketing, financial, risk-bearing and labour.
Assuming bigger is always cheaper.
Students remember only the falling part of the curve.
Fix: Remember the curve turns upward when management and coordination problems outweigh the gains.
Worked examples
Example 1
A large biscuit maker in Kolkata gets a lower interest rate on its loans than small bakeries because of its size. This is an example of: (A) External economy (B) Financial internal economy (C) Internal diseconomy (D) Technical internal economy
Show the solution
- Direction: the firm's cost of borrowing falls, so average cost falls. This is an economy, not a diseconomy.
- Source: the lower rate comes from the firm's own size, so it is internal.
- Type: the benefit relates to raising money, so it is a financial economy.
- Check options: A is wrong on source. C is wrong on direction. D is wrong on type.
Answer: (B) Financial internal economy
Example 2
A firm produces 1,000 units at a total cost of ₹50,000. After expansion it produces 2,500 units at a total cost of ₹1,00,000. Find the average cost before and after, and say whether the firm enjoys economies or diseconomies of scale.
Show the solution
- Average cost before = ₹50,000 ÷ 1,000 = ₹50 per unit.
- Average cost after = ₹1,00,000 ÷ 2,500 = ₹40 per unit.
- Average cost has fallen from ₹50 to ₹40 as output rose.
- A fall in average cost with higher output means economies of scale.
Answer: Average cost fell from ₹50 to ₹40, so the firm enjoys economies of scale.
Exam tips
- Most questions give a short example and ask you to classify it. Apply the two-question filter: direction, then source.
- Expect statement-type MCQs on internal versus external. Remember internal means one firm, external means the whole industry.
- Watch for options that swap 'economies' and 'diseconomies'. Check the direction of average cost first.
- Link the topic to the long-run average cost curve. A downward slope means economies and an upward slope means diseconomies.
- Since there is no negative marking, always attempt every question after eliminating wrong options.
Practice questions from Theory of Production
- In the long run, a firm moves through a stage of increasing returns to scale, then constant returns, and finally decreasing returns as it ex…
- A firm's production function is Q = 6L^0.5 K^0.5, where L is labour and K is capital. If both L and K are quadrupled, by what factor does ou…
- A Jaipur firm raises all inputs by 20% and its output rises by 30%. Which statement is correct?
- Which of the following is a diseconomy of scale that typically appears when a firm grows very large?
- In the theory of production, which of the following is classified as a fixed factor in the short run for a garment manufacturer in Tiruppur?
Economies and Diseconomies of Scale in other exams
The same ground in other exams, if you are preparing for more than one or want another angle on it.
Economies and Diseconomies of Scale: frequently asked questions
What is the difference between internal and external economies of scale?
Internal economies arise from the growth of an individual firm, such as bulk buying or better machines. External economies arise from the growth of the whole industry, such as a skilled labour pool or better infrastructure. Internal ones benefit only that firm. External ones benefit all firms in the industry.
What are the types of internal economies of scale?
The main types are technical, managerial, marketing, financial, risk-bearing and labour economies. Each is a different way a larger firm lowers its cost per unit. Learn one example for each type.
What causes diseconomies of scale?
Internal causes include slow decisions, weak coordination, poor worker morale and heavy supervision needs in a very large firm. External causes include congestion, higher rents and wages, and shortage of inputs when too many firms cluster together. Both push average cost up.
Do economies of scale go on forever?
No. After a certain size, the problems of managing a large firm can outweigh the gains. Average cost then stops falling and begins to rise, which is why the long-run average cost curve is usually U-shaped.