How the retirement map is built

*Page lives at theretirementatlas.com/methodology. Linked from the sample PDF page 8 ("Full terms and methodology"), the journey footer, and the Disclaimer. v1 draft prepared 2026-06-02. Curator voice. Observation, not advice. Sources named inline. Em dashes hard-banned.*

How the retirement map is built

This page explains how The Retirement Atlas turns the answers you give into the map you see. It is here so you can check our work.

What the map shows

The retirement map shows three things. An income gap, the difference between the retirement income your sources are likely to produce and the income your stated lifestyle would require. A plan odds figure, the share of historical market scenarios in which your plan survives the full period you selected without running out of money. And a set of observations about specific decisions you face, including when to claim Social Security, how Roth conversions interact with Medicare IRMAA tiers, what an old 401(k) means for your tax picture, and how a pension or annuity affects the income gap.

None of these are forecasts. None are recommendations. They are observations generated from the inputs you provided and the documented decision rules below.

Where the income gap comes from

Projected income sums Social Security at the claim age you entered, retirement account distributions at a 4 percent first-year rate adjusted forward, any pension or annuity income you reported, and any other income sources you listed.

Social Security is computed using the Social Security Administration's Primary Insurance Amount formula and the bend points published by the SSA for the current benefit year (ssa.gov, "Average Wage Indexing Series"). If you entered actual benefit estimates from your my Social Security account, we use those instead.

Retirement account withdrawals use the 4 percent first-year rate (Bengen, 1994, and updated by the Trinity Study and subsequent research) adjusted for the period before required minimum distributions begin under IRC Section 401(a)(9) as amended by SECURE 2.0 (the RMD age is currently 73, rising to 75 in 2033).

Projected need uses the lifestyle inputs you entered, inflated forward at the CPI-U rate published by the Bureau of Labor Statistics for the most recent twelve months (bls.gov, CPI-U series). We do not adjust for personal inflation experience; we use the national series.

The gap is the difference, expressed in today's dollars, in the first full year of retirement you selected.

Where plan odds come from

Plan odds are computed from a Monte Carlo simulation using 5,000 trials. Each trial samples annual real returns from the historical distribution of a 60 percent equity, 40 percent fixed income portfolio using monthly return data from Stocks, Bonds, Bills, and Inflation (SBBI, Ibbotson Associates) for the period 1926 through the most recent full year.

Each trial runs for the number of years between your selected retirement age and age 95 (the default planning horizon). Success is defined as ending the trial period with a portfolio balance greater than zero, after annual withdrawals, taxes on those withdrawals at the marginal rates you reported, and inflation adjustment.

The percentage shown is the share of trials that succeeded. We display it as a band (strong, middling, weak) rather than a precise number because the precision implied by a two-digit percentage is not warranted by the underlying model.

Where the observations come from

The observations are generated from documented decision rules, not from a recommendation engine.

IRMAA tier observations use the current Medicare Part B income-related monthly adjustment amount tiers published by CMS (cms.gov, "Medicare Costs"). Crossing a tier triggers a flag in the map.

Social Security earnings test observations use the SSA published earnings test thresholds for the current year (ssa.gov, "Receiving Benefits While Working").

Roth conversion observations use your reported marginal tax bracket and the projected impact on the current IRMAA tiers and the current ordinary income tax brackets (IRS Revenue Procedure for the current tax year). We do not forecast future tax law.

RMD observations use the IRS Uniform Lifetime Table from IRC Section 401(a)(9) and Treasury Regulation 1.401(a)(9)-9.

What we do not adjust for

We do not adjust the map for market movements during the day. We do not adjust for tax law changes that take effect between our publishing this page and your reading it. We do not adjust for your individual circumstances beyond what you have entered.

Small changes to inputs can produce meaningfully different results. The map is an illustration, not a forecast.

When this page is updated

This page is updated each time we change a source, an assumption, or a decision rule. The current version is stamped at the top of the page. Past versions are archived at /methodology/changelog.

Where to read more

Disclaimer: /disclaimer. Terms of Use: /terms. Privacy Policy: /privacy. Questions about a specific number in your map: methodology@theretirementatlas.com.

*Linked from the sample PDF page 8, the journey footer, the Disclaimer, and the homepage footer. Version stamp updates each time a source, an assumption, or a decision rule changes.*