Compounding

Asked to explain his fortune, Warren Buffett gave a three-part answer: “a combination of living in America, some lucky genes, and compound interest.” The third item is the only one anyone can copy. Munger’s contribution was a rule for protecting it — never interrupt compounding unnecessarily.

Why It Works

Compounding is growth applied to a base that itself keeps growing. Early on this is nearly invisible: 10% on a small number is a small number, and years of it feel like nothing is happening. Then the base gets large and the same percentage throws off gains that dwarf the original stake. Most of the total arrives late. Buffett made roughly 99% of his net worth after his 50th birthday — not because his returns improved, but because that’s when the curve turned steep.

The same mechanism runs outside money. Skills build on skills, a reputation compounds into better opportunities that build a better reputation, relationships deepen through accumulated small deposits. In all of these the shape is identical: a long flat stretch that tempts you to quit, followed by acceleration you can’t get back if you did.

The Cost of Interrupting

Because the late years carry the most weight — a second-order effect most people never run the math on — anything that resets the base is expensive out of proportion to its size. A tax event, a panic sale at the bottom, a two-year gap in a career, a blown-up friendship — each lops off not just what you had, but the decades of growth that amount would have produced. Munger’s “sit on your ass” investing is built entirely on this: the trading you skip protects the compounding you keep. A 20% return that gets interrupted every few years loses to a steady 12% that doesn’t.

Applying It

Start earlier than feels reasonable — a decade of lead time beats a higher rate. Then guard against the interruptions: automate contributions so they don’t depend on willpower, avoid unnecessary realized gains, and don’t sell a good position because the year was bad. In non-financial compounding, the equivalent is not letting a skill, a habit, or a key relationship go fully dormant; keeping a small process alive costs far less than restarting it cold.

The Broader Lesson

Munger treated compounding as a lens on almost everything worth doing: pick a vehicle that can run for decades — ideally one inside your circle of competence — feed it consistently, and get out of its way. The instinct it fights is the human preference for visible progress now. The payoff structure is the reverse — patience is not a virtue here so much as a term in the equation.

Sources

• ”a combination of living in America, some lucky genes, and compound interest” — Warren Buffett, The Giving Pledge letter, 2010
• ”never interrupt compounding unnecessarily” — attributed to Charlie Munger; widely quoted, see Poor Charlie’s Almanack
• Buffett earned ~99% of his net worth after age 50 — commonly cited figure, e.g. Morgan Housel, The Psychology of Money