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🎲 TOOL · What could this become?

What's Possible

Most tools show the dream as a smooth line. Reality is hundreds of bumpy futures — some great, some ruinous. This runs 500 of them and shows the whole spread, including how often it ends badly. Scrub the chart, pin a plan, compare.

How it works

The simulator

1 You describe a planWhat you start with, what you add, the return you are assuming, and how bumpy the ride is.
2 We run it 500 timesEach run gets its own random luck month by month, drawn around the return and bumpiness you set. Same plan, 500 different futures.
3 We show the whole spreadNot one number — the range they land in, and how often things go badly along the way.

Nothing here is a prediction. The return and bumpiness are numbers you type in. The tool has no idea whether they are achievable — it only works out what would follow if they were. Type an optimistic return and you get optimistic futures; that is arithmetic, not evidence.

The typical outcome lands below a straight-line calculation, and that is correct. Bumpiness costs you real money: a year of −30% followed by +30% leaves you down, not even. So a bumpy 12% a year does not compound like a smooth 12% — and the gap widens the wilder the ride.

“I’d quit at” is counted, but not acted on. A run counts as ruined if it ever falls that far from its peak — but it then carries on to the end and still counts towards the median, the range and the chart. So those headline figures include futures you said you would have walked away from, which makes them more optimistic, not less.

What this can’t tell you

A simulator is an argument about assumptions, not a look into the future.

  • It cannot tell you your assumed return is realistic. That number is the single biggest driver of everything on screen and it is pure input. Whether a real edge behind it is skill or luck is what Real or Noise? tests — a simulation built on an imaginary edge just draws an imaginary future very precisely.
  • The median is not a target. Half of the futures finish below it. Planning around the middle outcome means planning to be disappointed half the time.
  • The headline figures include runs you said you would have quit. Ruin counts a run that ever fell past your line, but that run keeps going and stays in the median and the range. A version where you actually stopped would look worse.
  • Luck is drawn from a bell curve. Real markets have fatter tails, crashes that arrive in clusters, and long flat stretches. Genuinely bad outcomes are more likely than this shows, not less.
  • No costs, no tax, no inflation. Trading costs come off every year (Cost of trading covers those), and a pound in ten years buys less than a pound today — so the ending figures flatter more the further out you look.
  • It assumes you keep paying in, all the way through, whatever happens. That is the assumption people break first, and usually at the worst moment.

Why the order of your luck matters

Both figures are the same money and the same years — only the order differs. One trader lives through the returns worst-first, the other best-first. Nothing else about them is different, so every pound of the gap is caused by sequence alone.

These are illustrative numbers, not a plan. The years are an invented alternating pattern used to make the effect visible, not real market history.

What this can’t tell you

The effect is real, but it points in a different direction at different stages of life.

  • It depends entirely on you still paying in. Stop the top-ups and the order stops mattering — multiplication does not care what sequence it happens in. The whole effect comes from how much money was there when each year landed.
  • Reverse it when you are taking money out and the conclusion flips. For someone drawing an income rather than contributing, bad years first is the dangerous case, because selling into a fall permanently removes the capital that would have recovered. Same maths, opposite lesson.
  • It does not mean you should hope for a crash. A bad run early only helps if you keep buying through it with money you can spare, and it is precisely then that most people stop.
  • The years here are a tidy pattern. Real returns do not alternate neatly good and bad, and real bad years arrive in clusters that last longer than one.
The thinking behind it
01
Compounding is slow, then sudden
READ →
02
Volatility is a tax on the ride
READ →
07
The order of your luck matters
READ →
Next

If that is the range, what are the odds of reaching a number you actually care about — and how long did it take the futures that got there?

Goal planner →