Eight yearly bars, each split into the principal, the interest it earned, and the interest that interest earned — the third band is the only one that curves. Evidence: compound against simple growth over forty years; the ladder is doubling time by rate.
The bigger it gets, the faster it grows
Roll a small snowball down a snowy hill. Each turn it picks up a bit of snow — and now it's bigger, so the next turn it picks up even more. Money in a savings jar that pays interest works the same: the interest you got last year earns its own interest this year, and the snowball speeds up on its own.
Start the snowball early — the hill is what does the work.
A = P · (1 + r / n)^(n·t)
Savings
1%
72 YEARS
Bonds
3%
24 YEARS
Equities
7%
10 YEARS
Card debt
12%
6 YEARS
Years to double at each rate, log-scale — the rule of 72