The Sixth Force Is Real: Why Complements Belong in Your Industry Analysis

The Five Forces Miss the Forest for the Trees

There's a stubborn myth in strategy circles that Michael Porter's Five Forces is the final word on industry analysis. I've lost count of the times I've seen a consultant or an MBA student run a Five Forces analysis, declare an industry unattractive, and then watch a company in that same industry mint money. The framework isn't wrong—it's incomplete. Porter himself has argued that complements are not a sixth force because their effect runs through the other five (Harvard Business Review). But Brandenburger and Nalebuff, the scholars who gave us the value net, make a compelling case that complements deserve equal footing with substitutes (Yale SOM). In an era where the global insights industry is worth over $150 billion and growing at 8% a year (ESOMAR), ignoring complements is like flying blind.

Imagine You're a Market Research Analyst Judging a Tech Giant

You're a senior analyst at a boutique research firm, and you've been asked to profile a major software company. Your boss wants to know whether the industry is attractive and whether the company's strategy is sound. You pull out the standard toolkit: Five Forces, PESTLE, SWOT. You dutifully note that the market research software sector is growing at 11.5%, while the mature market research services sector crawls at 4.8% (ESOMAR Global Market Research 2025). You see that the US holds a 53% share of the global market research market (Similarweb). You're tempted to conclude that software is the place to be, and the incumbents have high switching costs, so rivalry is moderate.

But here's what you'd miss: the software company's success depends on a thriving ecosystem of complementary products—data sources, AI tools, and even the hardware that runs it all. If you ignore complements, you'll misjudge the threat of substitutes and the power of buyers. You'll also miss the biggest strategic opportunity: partnering with complementors to raise customers' willingness to pay. As Brandenburger and Nalebuff note, a hardware industry needs a software industry to flourish, and vice versa (Yale SOM). That's not a side note; that's the core of modern tech competition.

Why Porter's Five Forces, on Its Own, Leads You Astray

Let's be clear: I'm not saying Porter is useless. The Five Forces framework, first presented in his 1979 HBR article, identifies the structural drivers of industry profitability (Harvard Business School). It's brilliant at showing how the economic value an industry creates gets apportioned among rivals, suppliers, customers, and the threat of entry or substitution (Harvard Business School). But it treats complements as an afterthought. Porter's 2008 article acknowledges complements but says their effect runs through the five forces (Harvard Business Review). That's technically true, but it's like saying gravity affects the stock market—true but not helpful for decision-making.

The problem is that in industries like software, media, and gaming, complements are often the primary source of value. Consider the giant market research industry itself. The research software sector grew 12.4% in 2023, while the traditional market research sector grew just 4.6% (ESOMAR via Research World). Software is a complement to research services—it makes them more efficient and scalable. If you analyze the research services industry without considering the software ecosystem, you'll overestimate the threat of substitutes and underestimate the power of suppliers (the software vendors). You'll conclude that research firms are squeezed, yet many are thriving by partnering with tech providers.

So, my recommendation is simple: when you profile a company, conduct a Five Forces analysis, but then explicitly add a sixth force: complements. Use the value net approach of Brandenburger and Nalebuff, which treats substitutes and complements symmetrically (Yale SOM). This isn't heresy; it's practical. It forces you to ask: who else benefits when my customer buys my product? Who else makes my product more valuable? And how can I partner with them instead of just competing?

Step-by-Step: How to Add Complements to Your Company Profile

Imagine you're profiling a mid-sized market research firm that's considering a move into AI-driven analytics. Here's how you'd apply the sixth-force lens.

Step 1: Map the value net. Draw a diagram with your company in the center. On one side, list your customers and suppliers. On the other side, list your substitutes and complementors. A complementor is any player whose product makes your offering more attractive (Yale SOM). For a research firm, complementors include data providers, survey platforms, and AI software vendors.

Step 2: Assess the power of complementors. Are they concentrated? Do they have high switching costs? In the research industry, the software sector is growing faster than services, and it's dominated by a few players. That gives software vendors considerable power over research firms—they can raise prices or bundle features that force research firms to adapt. In 2024, the research software sector grew about 11.5%, while the research services sector grew just 4.8% (ESOMAR Global Market Research 2025). That tells you software is a strategic bottleneck, not a minor accessory.

Step 3: Look for co-opetition opportunities. The value net's key insight is that business is a mix of competition and cooperation (Yale SOM). Instead of trying to build your own AI in-house, you might partner with a software vendor. That's how research firms can share in the growth of the software sector rather than being squeezed by it.

Step 4: Re-run your Five Forces with complements in mind. You'll likely find that the threat of substitutes changes. For example, if a software vendor offers a do-it-yourself survey tool, that's a substitute for your full-service research offerings. But if you partner with that vendor, you turn a substitute into a complement. The distinction is in your hands.

This process isn't just theoretical. The global insights industry is projected to surpass $160 billion by the end of 2025 (ESOMAR Global Market Research 2025). Companies that ignore the software ecosystem will be left with the low-growth, commoditized parts of the value chain.

Comparing the Two Frameworks: Five Forces vs. Six Forces

The table shows the key difference: Five Forces is a snapshot of industry structure; the value net is a map of your strategic relationships. Both are useful, but the sixth force is better for company profiling because it tells you who to work with, not just who to fight.

Common Objections (and Why They Fail)

You might object: 'Porter says complements aren't a sixth force, and he's the authority.' But authority isn't a substitute for logic. Brandenburger and Nalebuff show that substitutes and complements are symmetric up to a sign change, meaning they should be treated equally (Yale SOM). If you include one, you should include the other. Or you might say, 'We already consider complements in PESTLE.' But PESTLE is about macro trends, not industry structure. Complements are industry-specific and can change rapidly. For example, the US digital advertising market reached $258.6 billion in 2024, growing 14.9% (IAB/PwC). Advertising is a complement to free content—analyzing the media industry without considering advertising would be absurd. Yet Five Forces would miss it.

Some practitioners argue that adding a sixth force complicates analysis. My response: good. If your analysis doesn't capture the key drivers of profit, it's too simple. The industry analysis literature itself recommends combining frameworks—Porter for competition, PESTLE for macro trends (CFA Institute). Why not add complements? The marginal effort is small, and the insight can be huge.

Bottom Line

The single best move you can make next time you profile a company is to add complements as a sixth force. Don't just pay lip service to the idea—actively map your complementors, assess their power, and look for co-opetition opportunities. That's how you'll avoid the trap of declaring an industry unattractive when, in fact, the smartest players are collaborating their way to outsized profits. In a world where the insights industry is doubling every few years, you can't afford to ignore the force that's driving that growth.

Sources

• Harvard Business Review (Porter 2008) - https://hbr.org/2008/01/the-five-competitive-forces-that-shape-strategy
• Brandenburger & Nalebuff (Yale SOM) - 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
• Similarweb / Research and Markets - https://www.similarweb.com/blog/research/market-research/market-research-stats/
• CFA Institute - https://www.cfainstitute.org/insights/professional-learning/refresher-readings/2026/industry-and-competitive-analysis