IB Business Management HLUnit 1.5 — Growth and EvolutionPaper 1 & 2Core idea~11 min read
Why Bigger Is Cheaper, Until It Is Not
There is a reason a supermarket can sell a loaf for less than the corner shop pays for one. Size buys cheapness. But size also buys meetings, memos, layers of management and people who have never met each other trying to agree. Both halves of that story are examinable, and most students only revise the first half.
📘 What you need to know
Average cost = total cost ÷ output. It is the cost of making one unit, and it is the number this whole topic is about.
Economies of scale are the reasons average cost falls as output grows.
Internal economies come from inside the firm: financial, managerial, marketing, purchasing, technical, risk-bearing.
External economies come from the industry around it growing: clusters, transport links, a skilled labour pool, supportive legislation.
Diseconomies of scale are the reasons average cost starts to rise again: management, communication, geographical and cultural problems.
The lowest point on the curve is productive efficiency — the output where cost per unit is as low as it can get.
As output rises, total costs still increase. It is only the cost per unit that falls.
Start with average cost, or nothing else makes sense
Imagine a small bakery. Rent, the oven, the insurance and the manager’s salary all have to be paid whether it bakes 100 loaves a week or 10,000. Those are fixed costs, and they get spread across however many loaves come out.
The only formula you need here
average cost = total cost ÷ output
Bake 100 loaves against £500 of fixed costs and each loaf carries £5 of overhead. Bake 10,000 and each loaf carries five pence. Nothing about the oven changed. The cost simply had more units to sit on.
This is the sentence examiners are hunting for: costs of production are spread across more units of output. Write it in almost exactly those words and the mark is usually yours. It also protects you from the classic error of claiming that total costs fall as a firm grows — they do not.
The curve that runs the whole topic
Read it left to right: costs per unit fall while the firm is still getting better at being big, flatten at the efficient scale, then rise as the organisation gets harder to run.
Internal economies: getting cheaper from the inside
These come from the growth of the firm itself. Learn them as six labels with one mechanism each — the mechanism is what earns the mark, not the label.
Type
How it lowers average cost
A quick example
Financial
Large firms look safer to lenders, so they borrow at lower interest rates
A national chain pays 4% on a loan where a small shop pays 9%
Managerial
The firm can afford specialists instead of one person doing every job badly
A dedicated buyer negotiates better deals than a busy owner-manager
Marketing
One advertising campaign is spread across far more sales
The same television advert sells 5 million units instead of 50,000
Purchasing
Bulk orders attract discounts per unit from suppliers
Buying flour by the tonne rather than the sack
Technical
Expensive machinery runs closer to full capacity, spreading its cost
A production line worth millions running three shifts instead of one
Risk-bearing
A wider product range means one failure does not sink the firm
A drinks group selling twelve brands survives one brand falling out of fashion
Purchasing is the one to reach for first. It is the easiest to explain in one sentence and it applies to almost every case study. Just make sure you say the discount lowers the cost per unit, not the total spend.
External economies: getting cheaper because the industry grew
These have nothing to do with your firm’s own size. They happen because the whole industry around you expands, and you benefit whether you grew or not.
Source
What happens
Effect on average cost
Geographic cluster
Specialist suppliers and repairers move close to the main producers
Shorter supply lines and quicker fixes cut costs for everyone nearby
Transport links
Roads, rail and ports are improved to serve a growing industry
Cheaper, faster movement of materials, staff and finished goods
Skilled labour pool
Local colleges and rival firms train workers in the same skills
Less money spent on training and recruitment per employee
Favourable legislation
Government supports the sector with grants, tax relief or lighter rules
Direct reduction in the cost base of every firm in the industry
Three buckets, one question in each case: is average cost going down, and who caused it?
Diseconomies: when growth starts costing money
Past a certain size, the organisation itself becomes the problem. Nothing about the product changed; the difficulty of coordinating everyone did.
Type
What goes wrong
Why average cost rises
Management
Managers start protecting their own department rather than the firm
Duplicated roles, slow decisions, work done twice
Communication
More layers between the top and the shop floor
Instructions arrive late or distorted, so mistakes cost money
Geographical
Sites spread across regions or countries
Travel, logistics and coordination all add cost per unit
Cultural
New markets have different working norms and expectations
Disruption while the firm adjusts, especially early on
Diseconomies are almost always about people, not machines. If a case study mentions “several layers of management”, “staff feeling remote from head office” or “a merger of two very different companies”, the examiner has planted a diseconomies point for you to pick up.
🧩 How to answer an economies of scale question
Define it in cost-per-unit terms. Say average cost, not just “cheaper”.
Choose two types that genuinely fit the case study, and name them.
Explain the mechanism for each — what physically happens that makes the unit cheaper.
Link it to something the firm cares about: lower prices, higher margin, or capacity to compete.
If the question invites evaluation, bring in diseconomies and say what would trigger them here.
WORKED EXAMPLE
Calculating average cost before and after expansion
A furniture maker has fixed costs of £60,000 a year and variable costs of £40 per unit. It currently makes 2,000 units. After expanding it makes 6,000 units, and bulk buying cuts the variable cost to £34.
Before: total cost60,000 + (40 × 2,000) = 60,000 + 80,000 = £140,000Before: average cost140,000 ÷ 2,000 = £70 per unitAfter: total cost60,000 + (34 × 6,000) = 60,000 + 204,000 = £264,000After: average cost264,000 ÷ 6,000 = £44 per unitAverage cost falls from £70 to £44, a saving of £26 per unitnotice that total cost rose from £140,000 to £264,000 — that is exactly the distinction examiners test
EXAM-STYLE
Explain two economies of scale a growing coffee chain may benefit from. [4]
Purchasing economies
Ordering coffee beans and milk for 200 stores instead of 20 earns a discount per kilogram.
The same drink is then produced at a lower cost per cup.Marketing economiesone national campaign → spread over far more cups soldAdvertising cost per customer falls even though the total advertising budget has grown.Both work the same way: a cost is shared over a larger number of units
💡 Exam tip
Say “average cost” or “cost per unit” every time. Vague words like “cheaper” often miss the mark.
Never write that total costs fall. Growing output raises total costs; only the unit cost falls.
Label both axes if you draw the curve: average cost on the vertical, output on the horizontal.
Internal versus external is about the source. If the whole industry benefits, it is external.
Diseconomies are your evaluation. Mentioning them turns a 2-mark explanation into a proper judgement.
Pick economies that fit the firm — technical economies make no sense for a hairdresser.
⚠ Common mix-up
Economies of scale are not “spending less”. A firm enjoying them usually spends far more in total.
Diseconomies are not losses. A firm can be very profitable and still suffer rising average costs.
External economies do not require the firm to grow. They come from the industry expanding.
Risk-bearing is about product range, not about insurance.
The curve is not a demand curve. Price does not appear on it anywhere.
Productive efficiency is a point, not a range — the single lowest point on the curve.
Up next: Should a Business Grow at All? — we have shown that size cuts costs, so the obvious question is why so many firms deliberately stay small. The answer is more interesting than “they cannot afford to grow”.
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