The Eighth Wonder of the World
Einstein (allegedly) called compound interest the eighth wonder of the world. Whether he actually said it doesn't matter — the math is undeniably powerful.
¥10,000 growing at 15% annually becomes ¥10.83 million after 50 years. Not ¥75,000 (simple interest) — ¥10.83 MILLION. That's the power of compound growth.
The Compounding Table
| Years | 10% Return | 15% Return | 20% Return |
|---|---|---|---|
| 10 | ¥25,937 | ¥40,456 | ¥61,917 |
| 20 | ¥67,275 | ¥163,665 | ¥383,376 |
| 30 | ¥174,494 | ¥662,118 | ¥2,373,763 |
| 40 | ¥452,593 | ¥2,678,635 | ¥14,697,716 |
| 50 | ¥1,173,909 | ¥10,836,574 | ¥91,004,382 |
Notice: the difference between 10% and 15% seems small (just 5 percentage points), but over 50 years the outcome differs by 9x. Small edges compound into massive advantages.
Buffett's Living Proof
Warren Buffett's net worth reached $100B+. But here's the stunning fact: 99% of his wealth was earned after age 50. He started investing at 11 and became a millionaire at 30. But compounding really kicked in during the later decades.
"My wealth has come from a combination of living in America, some lucky genes, and compound interest."
The Three Enemies of Compounding
💡 What Kills Compound Growth
- Interruption — selling during downturns breaks the compounding chain
- High fees — a 2% annual fee sounds small but destroys 40% of returns over 30 years
- Impatience — switching strategies every year resets the clock to zero
- Taxes — frequent trading triggers short-term capital gains taxes
- Inflation — 3% inflation silently erodes purchasing power
Practical Implications
The most important variable isn't return rate — it's time. Starting 10 years earlier matters more than earning 5% more annually.
💡 Compounding Rules for Investors
- Start as early as possible — time is the most powerful variable
- Don't interrupt — let compounding work uninterrupted through market cycles
- Minimize friction — choose low-fee index funds or hold quality companies long-term
- Reinvest dividends — every dollar reinvested accelerates the snowball
- Be patient — the real magic happens in decades 3, 4, and 5
💡 Compound Interest — Key Summary
- ¥10K at 15% for 50 years = ¥10.83M (not ¥75K)
- Small differences in return rate create massive outcomes over time
- 99% of Buffett's wealth came after age 50 — compounding rewards patience
- The three enemies: interruption, fees, and impatience
- Start early, don't interrupt, minimize costs — let time do the work