Stress-test the complete plan
Rerun the plan using reordered historical market returns, keeping its income, expenses, taxes, and withdrawals connected.
Monte Carlo simulations
The future has more
than one path.
Explore how your plan holds up across hundreds of reordered historical market sequences. See the range, then look inside the runs that explain it.
Monte Carlo simulationsInside MoneyWhatIf
See what’s possible
How does your plan handle a bumpier journey?
Go beyond a single projection to see how different return sequences affect the years your money needs to cover.
Read the detailed guideSee the spread of outcomes
Explore the outcome range and the share of runs that avoid funding shortfalls.
Understand what happened
Inspect a lean, middle, or fortunate run to see the market sequence and the years behind its result.
Explore the details
Understand the history behind a market experiment
The historical simulator replays a chosen sequence, while Plan resilience explores many rearranged historical paths. The two tools answer complementary questions. One lets you examine a particular period and its timing; the other helps you see whether the plan’s result depends heavily on which path arrives.
- Use a chosen historical episode to investigate a specific concern.
- Use the simulation range to explore many possible sequences.
Historical market settingsInside MoneyWhatIf
From a question to a clearer picture
Explore the range, then open the runs
Plan resilience tests the whole household plan against rearranged historical returns. Use the headline to orient yourself, then investigate the paths behind it.
Choose the conditions to test
Select an index or an index timeline, including a change in allocation after retirement. Choose 100, 300, or 500 runs. Deal settings let you change how historical years are grouped and which inflation assumptions each run lives.
Run the connected plan through each history
Each run settles the household’s income, spending, taxes, withdrawals, and permitted sales. Read the split between runs that kept every home, needed a home sale, and ran short, alongside the share that avoided shortfalls.
Investigate the difficult outcomes
Select a run card or filter and sort Every run. Open a run’s complete projection to follow the market it encountered, the withdrawal years, and the point where money became tight. Use Deal it again to explore another set.
Connect the whole plan
Follow a difficult run into an ordinary year
A success rate summarizes many complete forecasts. Opening an individual run lets you examine the cash flow behind its outcome: which resources cover costs, what taxes are paid, and where money is invested. The flow view makes those annual mechanics easier to follow after selecting a run to investigate.
- Trace the funding sources in a year under pressure.
- Read the selected run’s assumptions with its annual results.
Money flowInside MoneyWhatIf
One way to use it · illustrative scenario
Test whether a smaller retirement budget helps
Imagine a couple who expect investment withdrawals to fund part of retirement. They want to explore the effect of reducing one discretionary expense while keeping their retirement dates unchanged.
Try an example planThe choice to explore
Start a What-If in the projection and lower their annual travel budget from $12,000 to $8,000. Open Plan resilience with the same market, sampling, and inflation choices.
Where to look
The comparison gives the original and edited plans identical futures. Examine the before-and-after outcome rate, which runs changed their ending, and whether difficult runs fail later or avoid a forced home sale.
What you could learn
The useful result is how that specific budget choice affects the tested paths. It provides a basis for discussing flexibility without turning a simulated success rate into a promise.
Make sense of what you see
Read beyond the headline percentage
Avoiding a shortfall can include a home sale
The outcome cards separate these experiences. A run that funds every year only after a permitted property sale counts as making it, while the sale remains visible as a different kind of retirement.
The fan summarizes one year at a time
The shaded bands show the spread across runs at each year. Their edges may belong to different runs from year to year. Choose an individual card to follow one complete path.
Lean, middle, and fortunate paths explain the spread
Run cards connect their ending balances with the history dealt around retirement. Compare the timing of losses and withdrawals, and check the money basis before interpreting large future-dollar balances.
A little more detail
Good questions to start with.
What does the give-or-take figure measure?
It describes sampling uncertainty in the share of runs that avoided shortfalls, using a Wilson 95% interval. It does not measure whether your inputs are correct or whether future markets resemble the historical record.
How are historical years rearranged?
The default uses blocks of up to 20 consecutive historical years, avoiding repeats where the available history allows. Shorter records can require reuse. Other methods include restarting history, rolling historical stretches, shorter blocks with replacement, and drawing years independently. The method can change the result.
Does running the test change my saved plan?
The page’s index, inflation, sampling, run-count, and deal settings do not overwrite the plan’s balances or return assumptions. Opening a selected run lets you inspect that scenario with the ordinary projection available for comparison.
Keep exploring
The next piece of your picture.
Historical market simulator
Replay historical market returns and explore how the timing of downturns changes your financial plan.
Retirement spending strategies
Compare retirement withdrawal strategies, including guardrails and variable percentage withdrawals, and see how spending responds to your portfolio.
Financial wellness
Read your forecast as a practical scorecard for savings, retirement readiness, and financial pressure points.
Know the language
Financial terms behind this feature
Rule of 25Lean FIREWealth PreservationSafe Withdrawal Rate (SWR)Trinity StudyThree-Fund PortfolioGlide PathDiversificationRebalancing60/40 PortfolioConsumer Price Index (CPI)DeflationMonte Carlo SimulationFIRE (Financial Independence, Retire Early)BogleheadWithdrawal Rate
Browse all financial termsYour next chapter
Bring your own what-if.
Start with your numbers. See where they could lead.