Morningstar's equity research team popularized a specific, widely used framework for where a genuine economic moat actually comes from: five distinct sources — network effect, switching costs, cost advantage, intangible assets (brand, patents, and regulatory licenses), and efficient scale. That last one is worth knowing on its own: efficient scale describes a market that's only large enough to profitably support one or a small handful of players — a single regional water utility or the only airport serving a smaller city are classic examples — where a new entrant would struggle to earn an adequate return even matching the incumbent's costs, simply because the market itself can't support the extra competition.
Identifying which of the five sources might apply to a company is only half the analysis. The other half is testing whether the claimed moat is actually real, and the most rigorous test is quantitative, not qualitative: sustained return on invested capital (ROIC) meaningfully above the company's cost of capital, persisting over many years without being competed away. Basic competitive dynamics predict that unusually high returns should attract competitors who erode those returns back toward the cost of capital over time — a company that keeps earning outsized returns for a decade or more despite that pressure is showing real, measurable evidence of a structural barrier, not just a good story.
Correct moves you up, wrong moves you down — reach 100 to master this lesson.