The stress test

The plan page assumes growth is exactly as you set it, every year. The stress test does not. It runs the same plan hundreds or thousands of times, drawing a different run of returns each time, and reports how often the money lasted. It is also called a Monte Carlo simulation. What varies, and what never does.

“Paid for everything” is the headline: the share of scenarios that funded everything you planned to the plan’s end. “Lasts as long as you do” sets the same scenarios against the chance each of you is still alive, from the ONS’s life tables. Beneath them, the fan shows the range your pots could land in, and the last card shows the spread of what could be left at the end.

The fan draws that range two ways. Bands shows the spread on its own. Scenarios draws the individual runs behind it, keeps the bands as dotted lines, and marks the year each run that fell short ran out.

The crash scenario is a different tool. It is one fixed bad run of returns that you choose and anchor to a year, with its own run of inflation if you set one. You set it on the Stress test page, and while it is on it shows on the plan page and runs inside every scenario. The stress test asks how luck varies. The crash asks what one particular run of bad luck would do.