Investing education, minus the hype
Learn how risk and return really work.
Buy Risk is a plain-language guide to investing. We explain the evidence-based models that actually move the needle (compounding, diversification, and the price of uncertainty), and give you interactive tools to feel them for yourself. Whenever possible, we pair simplified illustrations with simulations built on historical data.
See it in ten seconds
Every tool here works like this one: real data, one thing to drag, and the idea underneath made visible. Try it.
Over 1928–2025, that much compensated risk averaged about 8.9%/yr — through single years anywhere from about -21% to +39%.
Real US asset classes, 1928–2025. Volatility is the standard deviation of annual returns; return is their average. Only compensated risk pays: the kind nobody can sidestep, like the whole market falling at once. The risk that one company fails pays nothing extra, because owning many companies removes it for free — watch it disappear. The range above is the ride the average hides; the slope only pays if you can sit through the left end of it. And this is the US, one of the century's best-performing major markets, so treat these as upper bounds, not entitlements. Open the full tool →
The wiggly line is one possible decade. The shaded band is where $1 could reasonably end up: a thread when you take little risk, a funnel when you take a lot. Dragging the slider keeps the same run of luck and changes only how hard it hits you; New decade deals a fresh hand.
Turn the risk up and a second line splits off above. The lower line is the typical decade — the middle of the pack, what most people actually get. The upper one is the average, pulled up by a few very lucky decades. The gap opens because a 50% loss needs a 100% gain just to break even, so bad luck costs more than good luck pays. Both numbers are true at once. An illustration, not a forecast.
Pick a path
The tools build on each other. Follow a path in order, or jump straight to whatever question brought you here.
Path 1
Get your footing
Everything that comes before the first invested dollar — in order.
Path 2
How markets pay you
The evidence-based core: what return is, what erodes it, and who's really in the mirror.
Path 3
Build it, live with it
From ideas to an actual portfolio — and the decades after.
Prefer to browse? The full catalogs: interactive tools · personal finance · reference & live data · essays
Featured: the Bias Arcade
Test your own biases
Eleven two-minute experiments, adapted from the classic studies of behavioral economics, that measure your anchoring, loss aversion, overconfidence, herding, and more — before telling you what they were measuring. Play first; diagnosis after. Then watch your bias profile take shape.
Enter the arcade