Strategic Business Leader · Competitive forces

Porter's Five Forces Model for the ACCA SBL Exam

Updated 11 October 2026 · Fact-checked

Porter's Five Forces model analyses an industry through five pressures: threat of new entrants, supplier power, buyer power, threat of substitutes and competitive rivalry. Together they decide how much profit the industry can hold. To answer, assess each force from the case facts, rate its strength, then conclude on attractiveness and strategy.

Understand Porter's Five Forces Model

Porter's Five Forces is a tool for judging the attractiveness of an industry. Its core idea is that profit does not depend only on how good one firm is. It also depends on how much of the value created is taken by other parties: new competitors, suppliers, customers and rivals.

The five forces are:

Threat of new entrants: how easily new firms can enter and compete away profit.
Bargaining power of suppliers: how far suppliers can raise prices or cut quality and squeeze your margin.
Bargaining power of buyers: how far customers can push prices down or demand more for the same price.
Threat of substitutes: products from outside the industry that meet the same need in a different way.
Competitive rivalry: how intensely existing firms fight on price, features and marketing.

Strong forces mean low industry profit. Weak forces mean higher profit. So the model is not about listing forces. It is about judging how strong each is, and what that means for profit and strategy.

The model works at industry level, not company level. Define the industry first. A narrow or wide definition changes the answer. The model also helps you see where a firm can reposition itself, for example by building barriers, reducing dependence on a supplier, or differentiating to lower buyer power.

In SBL the model is a tool, not the answer. The examiner wants you to use it on the case, reach a judgement and link it to the organisation's strategic position and the task requirement.

Key rules to remember

Threat of new entrants: barriers to entry: Barriers high → threat low; barriers low → threat high; Typical barriers: economies of scale, capital requirements, brand loyalty and differentiation, switching costs, access to distribution, government policy, and expected retaliation by existing firms.
Supplier power: Supplier power is high when few suppliers dominate, inputs are unique or costly to switch from, and suppliers could integrate forward; Power is also higher when the industry is not an important customer to the supplier.
Buyer power: Buyer power is high when buyers are few or large, buy in volume, face low switching costs, and could integrate backward; Price sensitivity and full information on alternatives also raise buyer power.
Threat of substitutes: Substitute threat is high when a different product meets the same need at a comparable price and performance, with low switching cost; A substitute comes from outside the industry. A rival's similar product is not a substitute.
Competitive rivalry: Rivalry is intense when competitors are many and similar in size, growth is slow, fixed costs are high, products are undifferentiated and exit barriers are high; High exit barriers keep weak firms in the market and sustain price wars.
Industry attractiveness: The stronger the combined forces, the lower the potential industry profitability; Judge the overall picture. Do not just count forces.

How to solve Porter's Five Forces Model questions

Use this method for any five forces requirement in SBL, whether it asks you to analyse, assess attractiveness or advise on strategy.

1Read the requirement and decide what it is asking: a full analysis, the most important forces, or a recommendation. Note the role you are in and who the audience is.
2Define the industry and the organisation's position in it. Say which market you are analysing.
3Go through each force and pull specific facts from the case. Quote numbers, names and events rather than writing general theory.
4For each force, give a verdict: high, medium or low. Explain why in one or two sentences using the case facts.
5Identify which forces matter most. Rank them. Examiners reward judgement over equal coverage.
6Draw a conclusion on overall industry attractiveness and the effect on profit.
7Link to strategy: say how the organisation can respond, for example raise barriers, differentiate, or reduce supplier dependence. Tie back to the requirement.
8Check your professional skills: structure, clear communication in the requested format, and a balanced view of limitations if relevant.

Quickest way: Force, fact, verdict, so what

When to use it: Use this when time is tight and you need a structured answer in a few minutes, such as a short task or a part of a longer requirement.

Write the five force names down the page as a plan.
Next to each, jot one or two case facts that show strength or weakness.
Add H, M or L as your verdict.
Circle the one or two forces that hurt profit most.
Write each point as: force, case fact, verdict, consequence for the organisation.
Finish with one sentence on attractiveness and one on the recommended response.

Common mistakes in Porter's Five Forces Model

Listing theory for each force without using the case.
Students memorise the model and write what they know rather than what the scenario says.
Fix: Open each point with a case fact. Then give the verdict and the consequence.
Confusing substitutes with new entrants or rivals.
Both can take customers, so they feel alike.
Fix: A new entrant offers the same type of product and is a new firm in the industry. A substitute meets the same need in a different way from outside the industry. A rival is an existing firm in the industry.
Treating the model as company analysis instead of industry analysis.
The case is about one organisation, so students describe its strengths and weaknesses.
Fix: Define the industry first. Then assess forces facing all firms in it, and only afterwards comment on the organisation's position.
Giving every force equal space and no conclusion.
Students follow a checklist to feel safe.
Fix: Rank the forces and say which matter most. End with a view on profitability and a strategic response.
Using the model when the task asks for something else, such as the macro-environment or internal capability.
Five forces is a familiar tool and gets used by habit.
Fix: Match the framework to the requirement. Use PESTEL for the wider environment and capability tools for internal resources.
Ignoring that the model is static and omits other influences such as complementors or government.
Students treat the model as complete.
Fix: Where relevant, note limitations briefly, such as fast-changing markets, the role of regulation and complementary products.

Worked examples

Example 1

A regional airline operates short domestic routes. Facts: it needs expensive aircraft and airport slots are scarce; a high-speed rail link now runs between its two busiest cities at similar prices; several airlines compete on the same routes with similar fares; and it buys fuel at world market prices from a few large suppliers. Assess the threat of new entrants and the threat of substitutes.

Show the solution

Define the industry: short-haul domestic air travel.
New entrants: aircraft are expensive, so capital requirements are high. Scarce airport slots limit access. Both are barriers to entry.
Verdict on entrants: threat is low to medium, because barriers are strong, though a well-funded entrant could still obtain slots.
Substitutes: high-speed rail meets the same need, which is travel between cities, in a different way and from outside the industry.
Rail is at a similar price, so buyers have little cost to switch. That raises the threat.
Verdict on substitutes: high, particularly on the two busiest routes.
So what: the airline's profit is more exposed to rail than to new airlines. It should differentiate, for example on frequency, connections or service, on the affected routes.

Answer: Threat of new entrants is low to medium because of high capital needs and scarce slots. Threat of substitutes is high because high-speed rail offers a comparable service at a similar price on its busiest routes. Substitutes are the greater concern, and the airline should respond on those routes.

Example 2

A company makes branded smartphone cases. Facts: it sells mainly to three large retail chains that account for most of its sales; the chains can easily switch to other case makers; the cases are made from plastic sourced from many suppliers; and dozens of small firms sell similar cases. Explain the strength of buyer power and supplier power and the effect on profit.

Show the solution

Define the industry: manufacture and wholesale of smartphone cases.
Buyer power: three retailers take most of sales, so buyers are few and large. The firm depends on them.
Switching costs are low because the chains can move to other case makers. This raises buyer power further.
Verdict on buyers: high. The chains can press for lower prices or better terms.
Supplier power: plastic comes from many suppliers, so no single supplier has leverage and switching is easy.
Verdict on suppliers: low.
Effect on profit: strong buyer power takes margin away. Low supplier power does not offset it, as the main pressure is on the selling side. Dozens of similar rivals add to price pressure.
Response: reduce dependence on the three chains by finding new channels such as online sales, and differentiate through brand or design.

Answer: Buyer power is high because a few large retailers dominate sales and can switch easily. Supplier power is low because plastic is available from many sources. Overall, profit is squeezed mainly by buyers, so the firm should widen its customer base and differentiate its products.

Exam tips

Always tie each force to a fact in the case. Marks go to application, not recall.
Rank the forces and state which matter most. Then give a clear conclusion on industry attractiveness.
Keep the substitute versus new entrant distinction clean. A quick sentence defining each can stop you mixing them up.
Follow the format the task asks for, such as a report or briefing note, because professional skills marks depend on it.
Link your analysis to a recommendation or strategic implication, since SBL tasks usually ask what the organisation should do.

Practice questions from Competitive forces

Porter's Five Forces Model in other exams

The same ground in other exams, if you are preparing for more than one or want another angle on it.

Porter's Five Forces Model: frequently asked questions

What is the difference between threat of substitutes and threat of new entrants?

A new entrant is a new firm that enters your industry and offers a similar kind of product. A substitute is a different product from outside the industry that meets the same customer need. Barriers to entry limit entrants, while switching costs and relative price and performance shape the substitute threat.

How do I apply the five forces model to an SBL case study?

Define the industry, then take each force in turn and support it with facts from the case. Give a verdict on each, rank the most important, and conclude on profitability. Finish by linking to what the organisation should do.

Do I need to cover all five forces in every answer?

Not always. If the requirement asks about specific forces or the most significant ones, focus on those. If it asks for a full industry analysis, cover all five briefly and spend more time on the strongest.

Is Porter's Five Forces enough on its own in SBL?

Usually not. It is one tool for the external environment. It has limits, such as being static and industry-focused, so you often need to combine it with PESTEL, capability analysis or other models depending on the task.