File 03 — The Fog Behind the Number
The Fog Behind the Number
Your point estimate was never a point.
Say what you expect to grow — revenue, savings, a market — then admit you're not really sure of the rate. Ten thousand futures fan out across the years, each holding a different rate from your honest range, and the single confident number you'd have written in the plan comes apart into a spray. Draw the line you'd stake a decision on and watch how few futures actually clear it; nudge your best guess a single point and see the odds swing. Where The Monte Carlo Fan shakes the path around a return you claim to know, this shakes the return itself. Grounded in Knight, Taleb, Tetlock, and the overprecision literature.
Say what you expect, then admit you’re not sure of it — and watch your one confident number fan out into every future it was always hiding. Works for anything that compounds: revenue, savings, users, a market.
Drag this wider the less sure you really are. It’s not a guess at your confidence — it’s the span you’d put your name to.
What kind of surprises?
surprises are small and even. Try Crash risk and watch a few lines plunge — the rare disaster you never put in the plan.
Each faint line is one possible future — your best guess, but rolled forward at a different rate from your range. The bold lineis the single number you’d have written in the plan.
The red line on the chart. Your plan lands at €343k — drag right if the decision needs you to beat it, left if just surviving is enough. Futures ending above the red line are the ones where your bet pays.
Your plan
€343k
the one number you'd write down
Where most end up
€230k–€499k
the middle 90% of futures
Your bet pays in
50%
of ten thousand futures
A coin flip. Your call sits right in the middle of the spray — about as likely to miss as to hit.
And the answer barely holds still. Nudge your best guess up a single point — 8% to 9% — and your bet’s odds move by +11 points. One percent you couldn’t really be sure of, and the conclusion swings — that’s how much was resting on a number picked out of a fog.
Ten thousand futures, each handed one fixed growth rate drawn from your range, then compounded to the horizon. This is the mirror image of The Monte Carlo Fan, which shakes the path around a return you claim to know — here the return itselfis the thing you don’t know. Illustrative, not a forecast of any real business.
The essay
Your Number Was Never a Numberread →