Investing vs Gambling — Interactive Tools

Two small experiments about expected value and the law of large numbers, the ideas at the heart of the difference between investing and gambling. Pick one to explore.

Probability sandbox

The Marble Jar

Build a jar of winning and losing marbles, pull from it by hand, and watch your results converge toward the jar's expected value over thousands of draws. See why positive expected value rewards patience — and negative expected value punishes it.

Open the marble jar →
Historical data

S&P 500 — 20-Year Return Explorer

Pick any start year since 1928 and see how the S&P 500 performed over the following 20 years — nominal or inflation-adjusted, with or without dividends. A real-world look at how the law of large numbers plays out in markets.

Open the explorer →