An economic moat is a lasting competitive advantage that lets a company keep earning high profits while rivals try to take them away. The name comes from the water-filled ditch around a medieval castle: the business is the castle, and the moat makes it hard for competitors to attack. Warren Buffett popularised the image among investors. Morningstar's widely used framework groups the advantages into five sources: switching costs (customers find it a hassle to leave), network effects (the product gets more useful as more people use it), cost advantages (the company can produce or deliver more cheaply than others), intangible assets (brands, patents, licences) and efficient scale (a market so small that one or two players earn a fair profit and a newcomer would not). A moat is a judgement about the future, not a number you can read off a report.
Worked example
Say Company A has $100 million of money tied up in its business (factories, stock, software) and earns $12 million a year after tax from it, a return on invested capital (ROIC) of 12%. Investors who fund such a business ask for 8%, so the 8% is the bar to clear. Rivals in the same industry earn about 8%, because customers can switch to them easily. Company A earns 4 percentage points more: $12 million minus $8 million = $4 million a year above what the money is expected to earn. If customers stay loyal and rivals cannot copy the advantage, that gap can last for many years, and that lasting gap is what people mean by a moat. If the gap shrinks to zero over three years, there was no moat, only a good spell.
Why it matters
Investors care about a moat because profits that rivals can copy away do not last, while profits that are protected can keep growing for years. That makes a moat a useful question when you try to judge how long a company can keep earning well. The catch is that a moat cannot be measured directly. The usual clues are returns on capital that stay above the cost of capital for many years, steady profit margins and customers who do not leave, but each clue can also come from luck or a boom. Technology, new rules or a change in customer habits can also fill in a moat that looked wide. Treat the idea as a question to look into with the annual reports, not as a verdict, and remember that even a strong moat does not tell you whether the share price is reasonable.
Frequently asked questions
It is a lasting advantage that keeps competitors from taking away a company's profits, like the water-filled ditch around a castle. Common sources are switching costs, network effects, cost advantages, intangible assets such as brands and patents, and efficient scale.
You cannot read it off one number. Clues include returns on invested capital that stay above the cost of capital for many years, steady margins and customers who stay. Each clue can also come from luck, so treat it as a question to look into, not a verdict.
No. A moat describes the business, not the price. A company with a strong advantage can still trade at a price that already reflects it, and a moat can shrink over time if technology or rules change.
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