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Bellavia uses real market data (Shiller, JST, your own datasets, etc.) to test how your retirement plan would have performed across past economic conditions. This helps you see how your strategy stands up to different market environments including crashes, recessions, and bull markets.

Success Rate is the percentage of historical scenarios where your portfolio lasted the full retirement horizon without depleting. For example, a 95% success rate means your plan worked in 95 out of 100 tested scenarios. Higher success rates indicate more robust plans, but there's always a trade-off with spending levels. Note that this is an average of historical scenarios, not an average of independent histories.

Enter your starting portfolio value, select a retirement horizon (how many years), choose your asset allocation (stocks/bonds/cash), pick a withdrawal strategy, and click Calculate. Bellavia will test your plan against historical market data and show your success rate along with detailed charts.

The Retirement calculator simulates the decumulation phase—withdrawing from your portfolio during retirement. The Savings calculator simulates the accumulation phase—building wealth before retirement through regular contributions. Use Savings to plan how to reach your target, then Retirement to test if that target will last.

The default US dataset includes US and UK data from 1900 to 2020 (120 years). Other datasets that you can load like Shiller and JST Macrohistory cover different time periods and markets. Each dataset captures different economic eras including world wars, the Great Depression, stagflation, and modern market cycles.

Withdrawal strategies determine how much you take from your portfolio each year. Options include:

• Constant Amount: A fixed dollar withdrawal each year
• Fixed Percentage: A set % of portfolio value each year
• Inflation Adjusted: Withdrawals that track inflation (the classic 4% rule)
• Guardrails: Withdrawals that adjust within limits based on portfolio performance
• 95% Rule: Never withdraw more than 95% of last year's amount
• 1/N Strategy: Divide portfolio by remaining years

The 4% Rule suggests withdrawing 4% of your initial portfolio in year one, then adjusting that amount for inflation each year. It was derived from the Trinity Study and historically provided a high success rate over 30-year periods with a 50/50 stock/bond portfolio. In Bellavia, this corresponds to the Inflation Adjusted strategy with a 4% initial rate.

Use Guardrails if you want spending flexibility. It increases withdrawals when markets do well and reduces them during downturns, within limits you set. This approach can improve success rates while allowing you to enjoy more spending in good years. It requires comfort with variable income.

The 95% Rule (also called the Ratchet Rule) means you never withdraw more than 95% of last year's withdrawal, even if your regular strategy would suggest higher spending. This protects against overspending after a single good year and creates a smoother spending path during volatile markets.

The 1/N Strategy divides your portfolio by the number of remaining years. With 20 years left, you withdraw 1/20th (5%) of the current portfolio value. As years decrease, the percentage increases. This strategy automatically adjusts to portfolio performance and guarantees your money lasts exactly N years, but spending varies significantly year to year.

Yes. Use Extra Cash Flows to add Social Security, pensions, rental income, or part-time work. Bellavia subtracts these income sources from your required withdrawal, reducing portfolio strain. You can set start and end ages for each cash flow to model delayed Social Security or temporary income.

Sequence-of-returns risk is the danger that poor returns in early retirement, combined with withdrawals, can permanently damage your portfolio—even if long-term averages are good. A retiree who experiences a crash in year one faces worse outcomes than one who experiences the same crash in year 20. Timing matters as much as averages.

Drawdown Analysis shows how far your portfolio might fall from its peak during retirement. It displays maximum drawdown percentages, how long drawdowns lasted, and recovery times across all historical scenarios. This helps you understand the emotional and financial stress you might face during market downturns.

The Market Regimes chart shows how your plan performed during different market conditions: bull markets, bear markets, and sideways/volatile periods. It helps you understand if your strategy is robust across all conditions or if it only works in favorable environments. Look for consistent success rates across all regimes.

Terminal Value Distribution shows what your portfolio might be worth at the end of your retirement horizon across all tested scenarios. It's a histogram of ending values, from $0 (plan failed) to potentially much higher than your starting amount. This helps you understand both failure risk and legacy potential.

Real dollars (inflation-adjusted) show your true purchasing power over time. Nominal dollars show raw account balances without inflation adjustment. Most users find real dollars more meaningful because $1 million in 30 years won't buy what $1 million buys today. Bellavia defaults to real dollars for this reason.

Bellavia supports different historical datasets. There are two default datasets for the US and the UK. There are international options via the JST Macrohistory Database. Each dataset captures different market characteristics. US data has the longest history; international data provides geographic diversification in testing.

Premium/Pro/Enterprise users can upload custom datasets in CSV format. This allows testing against specific market data, custom asset classes, or proprietary return series. The upload wizard validates your data format and provides guidance on required columns (year, returns, inflation).

Different markets have different historical return patterns, volatility, and inflation experiences. US markets have generally outperformed other developed markets over long periods, so US-based results tend to be more optimistic. Testing across multiple datasets gives a more complete picture of possible outcomes.

Click the Save button after running a simulation to store your configuration. The number of available slots depends on your subscription level. Saved configurations include all your inputs: portfolio value, allocation, withdrawal strategy, extra cash flows, and settings. Load them anytime to rerun or modify.

Premium includes advanced analytics (drawdown analysis, market regimes, sequence risk charts), save slots, custom dataset uploads, Monte Carlo simulations, PDF report generation. Visit the Pricing page for full details and current pricing.

Use the Extra Cash Flows section below the main inputs. Click Add Income, enter the annual amount, set the start time (e.g., 7 if Social Security starts in the 7th year of retirement), and optionally set an end time. You can add multiple income sources and expenses. These are automatically factored into your withdrawal calculations.

Yes. Pro users can access the Bellavia API to run simulations programmatically. The API supports all simulation parameters and returns detailed results in JSON format. This is useful for financial advisors running batch analyses, developers building integrations, or researchers conducting studies. More details here.