Porter's five forces explained, with a worked industry example

Porter’s five forces is a framework for judging how profitable an industry is likely to be, by looking at the pressures that push prices down and costs up. Introduced by Harvard Business School professor Michael Porter in a 1979 Harvard Business Review article, it remains one of the most widely taught tools in business strategy. The core insight is simple: competition for profits comes not only from direct rivals but also from customers, suppliers, potential entrants and substitute products.

Why industry structure matters

Some industries earn high returns year after year while others struggle no matter how well they are managed. Porter’s argument is that the difference comes mainly from industry structure, meaning the underlying economic and technical features that shape how value gets divided. A company can be brilliantly run and still earn thin margins if it sits in a structurally tough industry.

The Institute for Strategy and Competitiveness at Harvard Business School puts it this way: the five forces determine an industry’s average profitability, and understanding them is the starting point for positioning a company within it. That is why the framework belongs at the business-unit level of corporate strategy: it tells you where profits are available before you decide how to compete for them.

The five forces, one by one

1. Threat of new entrants

New competitors bring fresh capacity and a desire to win market share, which pushes prices down and costs up. What matters is not how many companies actually enter but how credible the threat is. That depends on barriers to entry, the obstacles a newcomer must overcome. Common barriers include economies of scale, high capital requirements, strong brands and customer loyalty, switching costs, access to distribution channels, patents and government licensing.

2. Bargaining power of suppliers

Powerful suppliers capture more value for themselves by charging higher prices, limiting quality or shifting costs onto their customers. Supplier power is high when a few suppliers dominate, when their product is essential and hard to replace, when switching suppliers is costly, or when the supplier could plausibly enter the buyer’s industry itself. Labor counts as a supplier too, so a highly skilled or unionized workforce can be a powerful force.

3. Bargaining power of buyers

The mirror image of supplier power. Powerful customers force prices down, demand better quality or more service, and play suppliers off against each other. Buyers have leverage when they are few and large relative to sellers, when products are standardized, when switching costs are low, and when buyers are price-sensitive because the purchase is a big share of their own costs.

4. Threat of substitutes

A substitute performs the same or a similar function by a different means. Video calls substitute for business travel; a home espresso machine substitutes for a café. Substitutes put a ceiling on prices: if an industry charges too much, customers switch. The threat is greatest when the substitute offers an attractive price-performance trade-off and switching is easy. Substitutes are easy to overlook because they often come from outside the industry.

5. Rivalry among existing competitors

Rivalry shows up as price cuts, new product launches, advertising campaigns and service improvements. It is most damaging when it turns into price competition, because that transfers profit directly to customers. Rivalry tends to be intense when there are many competitors of similar size, industry growth is slow, products are hard to tell apart, exit barriers are high and fixed costs push companies to fill capacity at almost any price.

Factors that are not forces

Porter’s 2008 article is clear that several things people often add to the list are better understood as factors that work through the five forces. Industry growth rate is one: fast growth can ease rivalry for a while, but it says nothing about whether suppliers or buyers will capture the gains. Technology and innovation are another, since a new technology matters only insofar as it lowers entry barriers, creates substitutes or shifts bargaining power. The same goes for government regulation and complementary products, goods or services used alongside an industry’s own, such as software for computers. Treating these as separate forces risks double-counting; asking how each one changes the five forces keeps the analysis sharp.

A worked example: the airline industry

Airlines are a textbook case, and Porter himself uses the industry as an example of structural difficulty in his 2008 update. Here is a simplified, general assessment:

Force	Strength	Why
Threat of new entrants	Medium	Aircraft can be leased, but airport slots, regulation and scale are real barriers
Supplier power	High	Few large aircraft and engine makers; powerful unions; airports with local monopolies
Buyer power	High	Fare comparison is easy online, many travelers are price-sensitive, switching costs are low
Threat of substitutes	Medium	Trains, cars and video calls replace some trips, especially short ones
Rivalry	High	High fixed costs, perishable seats and similar products encourage fare wars

The picture explains why airlines can carry millions of passengers and still struggle to earn returns above their cost of capital over long periods. Value leaks to aircraft makers, airports, labor, and price-sensitive customers. The forces also suggest where airlines try to fight back: loyalty programs raise switching costs, alliances and consolidation reduce rivalry, and fees for extras let carriers advertise low fares while recovering revenue.

Contrast that with an industry where entry is hard, buyers are fragmented and substitutes are weak. Profits there tend to be higher and steadier, even for average competitors.

How to run a five forces analysis

1. Define the industry. Be specific about the product and the geography. “Restaurants” is too broad; “quick-service pizza delivery in a mid-size US city” is workable.
2. Identify the players behind each force: competitors, buyers, suppliers, possible entrants and substitutes.
3. Rate the strength of each force and note the evidence. Use data where you can, such as market shares, supplier concentration and price trends.
4. Find the strongest forces. These set the ceiling on profitability.
5. Look ahead. Ask how each force is likely to change over the next few years and why.
6. Turn it into strategy. Look for a position where the forces are weakest, or ways to reshape them in your favor.

The SBA’s guide to market research and competitive analysis offers practical ways to gather the underlying information, and the results feed directly into the market analysis section of a business plan.

Limitations of the model

The framework is powerful, but it has well-known weak spots:

• It is a snapshot. It describes structure at a moment in time, while technology and regulation can reshape forces quickly. Always add a forward-looking view.
• Industry boundaries blur. In digital markets, it can be hard to say who the competitors, buyers and substitutes are, especially for platforms that serve several customer groups at once.
• It underplays cooperation. Companies also create value through partnerships and complementary products. Porter’s 2008 article treats complements and government as factors that act through the five forces rather than as forces themselves.
• It explains industries, not companies. Two companies in the same industry face the same forces but can earn very different returns. The model needs to be paired with an analysis of each company’s own strengths.
• It is qualitative. Ratings such as “high” and “medium” involve judgment, so two analysts can reach different conclusions.

Complements: SWOT and PESTEL

Five forces works best as one tool among several:

• PESTEL scans the wider environment: Political, Economic, Social, Technological, Environmental and Legal factors. It helps spot shifts, such as new regulation or demographic change, that will alter the five forces over time.
• SWOT looks at a single company’s Strengths and Weaknesses (internal) and Opportunities and Threats (external). The five forces analysis feeds the external half.
• Value chain analysis, another Porter tool, looks inside the company at the activities that create value and cost.

A sensible sequence is PESTEL for the big picture, five forces for the industry, then SWOT and value chain analysis for the company.

The bottom line

Porter’s five forces explains why profitability differs so much between industries: the more power entrants, suppliers, buyers, substitutes and rivals have, the less value is left for the companies in the middle. Use it to understand where profits come from and where they leak, then pair it with company-level tools to decide how to compete. For more strategy explainers, browse our Business & Strategy hub.