Mental model
Moats and Durable Competitive Advantage
A great business is one protected by a durable advantage — a 'moat' that keeps competitors from eroding its returns over time.
Munger’s central contribution to Berkshire’s investing was the shift from buying cheap, mediocre businesses to buying great ones at fair prices — and what makes a business great is a durable competitive advantage. The metaphor is a castle with a moat: most businesses earning high returns attract competitors who copy them and compete the profits away, so the rare and valuable thing is a barrier wide and deep enough that rivals cannot easily cross it. That barrier is what lets a company keep earning unusually good returns for a long time.
Moats come in a few recognizable forms: a brand customers trust and will pay up for, a network that gets more valuable as more people use it, a cost advantage competitors can’t match, high switching costs that lock customers in, or a regulatory or scale position that’s hard to assail. See’s Candies — the 1972 purchase Munger pushed Buffett toward — is the archetype: a beloved brand with pricing power that competitors could not dislodge, throwing off cash for decades. The quality of the moat, not the cheapness of the price, was the point.
The word that matters most is “durable.” Plenty of companies enjoy a temporary advantage that looks like a moat and then evaporates when technology or tastes shift; Munger was wary of those. The hard judgment is whether an advantage will still be standing in ten or twenty years, and most won’t be — which is why truly moated businesses are rare and worth holding once found. This model connects directly to sit-on-your-ass investing: the reason you can buy a wonderful business and simply keep it is that the moat does the work of protecting your returns while you do nothing.
