Michael Porter (born 1947) is a Harvard Business School economist who gave competitive strategy a formal structure. His work explains why some industries are more profitable than others and why, within an industry, some firms sustain higher returns.

The five forces

Competitive Strategy (1980) argued that an industry's profitability is set by five forces: rivalry among existing competitors, the threat of new entrants, the threat of substitutes, and the bargaining power of suppliers and of buyers.

The practical consequence is that industry structure, not effort, explains most of the variation in returns. A well-run firm in a structurally poor industry can work harder than a mediocre firm in a good one and earn less. Strategy begins by assessing the forces and then choosing a position that is defensible against them.

Generic strategies and the value chain

Porter argued that a firm sustains advantage either by cost leadership or by differentiation, and that attempting both leaves a firm stuck in the middle with neither. Focus — applying one of the two to a narrow segment — is the third option.

Competitive Advantage (1985) introduced the value chain: the sequence of activities through which a firm creates value. Advantage comes from performing activities differently or performing different activities, which locates strategy in operations rather than in a statement of intent.

Strategy as choice

His most quoted claim is that the essence of strategy is choosing what not to do. A position that involves no trade-offs can be copied by anyone, so sustainable advantage requires accepting some disadvantage. Competitors who want the benefit must give up something they are unwilling to give up, which is what makes the position hold.

Criticism

Critics argue the framework suits stable industries better than fast-moving ones, and that it describes how to defend a position more convincingly than how to create one. Both objections are widely accepted without displacing the framework, which remains the standard vocabulary for the subject.