Why Your Supply Chain Analysis Is Missing the Sixth Force

Imagine you are a procurement director at a mid-sized electronics manufacturer. Your team has just completed a Porter's Five Forces analysis of your key component suppliers. The results show moderate supplier power, low threat of new entrants, and intense rivalry among your existing suppliers. You feel confident. Then a new software platform emerges that integrates with your suppliers' systems, making it far easier for you to switch between them. Your carefully calculated supplier power just evaporated. What did you miss?

You missed the complements. In the classic five-forces view, complements are products or services used together with your industry's product, but they are not treated as a separate force—their effect runs through the other forces (Porter 2008). But Brandenburger and Nalebuff, in their Yale working paper, argue that complements deserve equal footing: because substitution and complementarity are symmetric, they should be treated as a force on exactly the same footing as substitutes (Brandenburger & Nalebuff). In supply chain analysis, that distinction is not academic. It changes how you map risk and opportunity.

We tend to analyze our supply chains with a static lens: who are my suppliers, what are their prices, how much power do they hold? But the real world is dynamic. A complementor—a player whose product makes your offering more attractive—can be a supplier, a customer, or even a competitor's ally. For a hardware company, the software ecosystem is a complementor: without it, your hardware is less valuable. In supply chains, complements often appear as logistics platforms, data providers, or standards bodies. They can shift the balance of power overnight.

So the question we need to answer is not whether complements are a sixth force—they are, in the logic of the value net—but how to identify them and factor them into our supply chain decisions. Here is a practical approach.

Start with the Value Net, Not the Value Chain

Porter's value chain is a useful tool for understanding internal activities, but it is inherently firm-centric. It divides your activities into primary and support categories, and it helps you see where you can cut costs or differentiate (IBM Think). But it does not capture the network of players around you. Brandenburger and Nalebuff's value net does. It maps four types of players: customers, suppliers, substitutors, and complementors. In a supply chain context, your suppliers are obvious, but your complementors might be the software vendors that connect you to your suppliers, the logistics providers that make just-in-time delivery possible, or even the regulators that set standards.

Consider the market research industry itself. ESOMAR estimates the global insights industry surpassed $150 billion in 2024 and will surpass $160 billion by 2025 (ESOMAR via Research World). The research software sector alone was about $62 billion in 2024, growing at 11.5%, while the mature market research sector grew only 4.8% (ESOMAR via Research World). If you are a traditional market research firm, your software vendors are not just suppliers—they are complementors. Their tools determine how easily you can deliver insights. If a software provider makes it easy for your clients to switch to a DIY platform, that software vendor is simultaneously a complementor and a threat. In the value net, that dual role is explicit.

Map Your Complementors and Their Power

Once you see complementors as a force, you need to assess their power. Ask: How concentrated are my complementors? What switching costs do I face if I change them? Do they have alternative customers? This mirrors the questions you would ask about suppliers, but with a twist: complementors often operate in adjacent markets, so their incentives may not align with yours. A classic example is a hardware manufacturer that depends on a dominant software platform. The platform is a complementor, but it can also become a bottleneck if it decides to favor a rival hardware maker.

In supply chains, this is especially true for data and analytics providers. The ICC/ESOMAR International Code, established in 1977, sets ethical standards for research, but it does not address the power dynamics of data access. Yet data is the lifeblood of modern supply chain analysis. If your key logistics data provider is acquired by a competitor, that complementor just turned into a substitutor. You need to identify which complementors are critical and how easily they could switch sides.

Assess the Impact on the Five Forces

Porter is not wrong to say that complements affect profitability through the five forces. For example, a strong complementor base can increase buyer power if it gives customers more options. But treating complements as a separate force forces you to ask questions you might otherwise miss. When you analyze supplier power, you look at concentration, switching costs, and the availability of substitutes. With complements, you also need to look at network effects. Demand-side benefits of scale, or network effects, arise when a buyer's willingness to pay increases with the number of other buyers (Porter 2008). In supply chains, this can create a virtuous cycle: as more suppliers adopt a particular data standard, it becomes more valuable for you to adopt it too, locking you in.

That lock-in can be beneficial or detrimental. If you are the one benefiting from the network effect, it is a barrier to new entrants. But if you are dependent on a complementor's network, that dependency is a risk. Consider the Herfindahl-Hirschman Index (HHI), which the US Department of Justice uses to measure market concentration. A market with an HHI above 1,800 is considered highly concentrated (US DOJ Antitrust Division). If your complementor market is highly concentrated, you have less negotiating room. That is a red flag for your supply chain resilience.

Make Complements a Formal Part of Your Analysis

In practice, this means adding a column to your industry analysis spreadsheet. For each key input or service, list not only your suppliers but also the complementors that enable them. Then score their power using the same criteria you use for suppliers: concentration, switching costs, and the availability of substitutes. This does not require a Ph.D. in economics—just a structured way to ask the question.

One concrete example: imagine you are a pharmaceutical company. Your suppliers include active pharmaceutical ingredient (API) manufacturers. Your complementors might include clinical research organizations (CROs) that conduct trials for your drugs. If there are only a few large CROs, they have significant power over your time-to-market. That power is not captured in a traditional supplier analysis of API manufacturers. Yet it can determine your competitive position. The ESOMAR data shows that pharmaceutical companies account for about 16.6% of market research spending (Similarweb / Research and Markets), so they clearly understand the value of insights. But they might not be applying the same rigor to their supply chain complementors.

Another example: the US digital advertising market reached $258.6 billion in 2024, up 14.9% year over year (IAB/PwC). If you are in that industry, your supply chain includes data providers, ad servers, and measurement firms. Many of these are complementors. A change in one—say, a new privacy regulation—can ripple through the entire ecosystem. That is why you need to monitor not just your direct suppliers but the complementors that shape their behavior.

To make this work, you need to embed the analysis in your regular strategic review. The CFA Institute recommends using both Porter's Five Forces and PESTLE to understand the competitive environment (CFA Institute). We should add complements to that toolkit. Not as a footnote, but as a full-fledged force. The value net is not a replacement for the five forces; it is an extension that makes the framework more logically complete (Brandenburger & Nalebuff). In a world where supply chains are increasingly digital and interconnected, ignoring complements is like navigating with a map that misses half the terrain.

Bottom line

Do not just analyze your suppliers. Map your complementors—the software, data, and services that make your supply chain work—and treat them as a force with the same weight as Porter's five. The single best move you can make is to add a complementor analysis to your next industry review. It could save you from the next disruption that no one saw coming.

Sources

• Brandenburger & Nalebuff (Yale SOM paper) - https://som.yale.edu/sites/default/files/2024-12/1-SYMMETRY-AND-THE-SIXTH-FORCE-THE-ESSENTIAL-ROLE-OF-COMPLEMENTS-Adam-Brandenburger-Barry-Nalebuff%202.pdf
• ESOMAR via Research World (GMR 2025) - https://researchworld.com/articles/inside-the-153bn-insights-industry
• Harvard Business Review (Porter 2008) - https://hbr.org/2008/01/the-five-competitive-forces-that-shape-strategy
• IBM Think - https://www.ibm.com/think/topics/value-chain-analysis
• US DOJ Antitrust Division - https://www.justice.gov/atr/herfindahl-hirschman-index