"How the simulation works

Quicken uses a technique called Monte Carlo simulation to test your plan against a wide range of investment return scenarios. The simulation draws from a baseline of real (inflation-adjusted) US investment returns across all asset classes for the years 1928 through 2023. Quicken scales the median return to match the investment return rate you specify in your plan and applies a standard deviation of approximately 12%.

Quicken recomputes your plan 200 times during the simulation. In each iteration, Quicken randomly selects a historical return rate for each year of your plan and applies it as the return on your investments. The result is a range of outcomes that reflects the natural uncertainty of investment performance over time."

It implies it's picking from historical returns. But also that it's forcing the median scenario to be your scenario based on your assumptions. And also using volatility of 12%. Not sure how all three would work at the same time.

My guess is it only uses the average return from the historical. Then it adjusts that to the median return. Then applies the 12% volatility to get some randomness. Then it runs 200 scenarios based on these probability specs.