What an economic moat is

An economic moat is a durable competitive advantage that protects a company's profits from competitors, the way a moat protects a castle. The term was popularised by investor Warren Buffett, and it is one of the most powerful ideas in fundamental analysis.

Why moats matter so much

Capitalism is brutally efficient. When a company earns high returns, rivals are drawn in like water flowing downhill, competing those returns away until the business earns only an ordinary return. A moat is what stops that from happening — it lets a company keep earning high returns year after year while competitors fail to break in.

This is the difference between a good company and a good investment. A company with no moat can be excellent today and mediocre in five years once competitors copy it. A company with a wide moat can compound returns for decades, and that durability is exactly what makes long-term ownership work.

The signature of a moat

You can often spot a moat in the numbers before you can name its source: persistently high returns and margins that do not erode over many years, even as the company grows and rivals try to attack. If a business has earned strong, stable profitability through multiple cycles, something is protecting it — your job is to identify what, because a moat you cannot explain may be an illusion about to vanish.

The next lessons walk through the five classic sources of a moat, then how to judge whether a given moat will actually last.