Studies
When to claim Social Security if the 2033 reduction happens: 62 vs 67 vs 70
Under the 2026 Trustees projection (78% of scheduled benefits payable from 2033), the lifetime-value-maximizing claiming age falls from 70 to 68 in the base case across 18 profiles, and the classic 62-vs-70 break-even stretches from age 80 to 82. Includes an after-tax and tax-torpedo view.
What a 22% Social Security cut does to retirement success: a 10,000-path Monte Carlo study
When half of income comes from Social Security, a 2033 reduction is a 15.3-point fall in success rate for a 60/40 retiree — offset by roughly $122,768 more saved. Modeled across three allocations and three reliance levels, per the 2026 Trustees Report.
What crossing an IRMAA tier costs a Roth conversion: 2026, tier by tier
The Medicare surcharge is a fixed-dollar cliff two years later, so a small conversion that just clips a new tier is punished hardest per dollar. This study prices the first dollar over every 2026 tier, the room to the next one, and when crossing still beats leaving the money for future RMDs.
Dynamic vs. static withdrawal strategies, quantified
Four withdrawal rules — the static 4% rule, a constant 5%-of-balance rule, Guyton-Klinger guardrails, and Variable Percentage Withdrawal — run on the same 10,000 Monte Carlo paths over 35 years. The guardrail plan cuts the 4% rule’s failure rate from 17% to 1.1% — a 94% reduction, by trading depletion for spending cuts — at about 40% less median legacy.
The 2026 ACA subsidy cliff for early retirees: an 80,000-path Monte Carlo study
Modeling a 55-to-65 healthcare bridge with 2026 tax and ACA parameters, the study measures what the subsidy cliff costs a retiree who does not manage MAGI — and how much a tax-optimized withdrawal order recovers.
Social Security at 70 beats 62 only 42% of the time — if you invest
A 400,000-life Monte Carlo over real mortality (SSA 2021 Period Life Table) and real investment returns shows the famous age-80 break-even hides a coin flip: at a balanced 4% real return, delaying wins 42% of lifetimes; at an equity-tilted 6% real return, only 28% for men.
Retiring into a bear market: same plan, 46% failure vs. 0%
A 50,000-path block-bootstrap Monte Carlo of U.S. historical returns (1928–2024) isolates sequence-of-returns risk by holding the plan fixed and only reordering the first decade. A reversed 1973–2002 sequence with the identical average return leaves 6× more terminal wealth than the forward order.
Does the 4% rule survive forward-looking forecasts? Six published CMEs stress-tested
10,000-path Monte Carlo simulations of a classic $1M, 60/40, 4% inflation-adjusted withdrawal with no other income, run under six publicly-published Capital Market Expectations. Against a 95.9% historical baseline every forecast lands lower, and among the survivors median terminal balance spans 2.3× — a plan’s safety margin depends heavily on which return assumption it borrows.
The lifetime tax cost of skipping Roth conversions in the gap years
A deterministic federal-tax simulation (2025 MFJ brackets, SECURE 2.0 RMD age 73) compares doing nothing with a Traditional IRA against filling the 12% bracket with Roth conversions before RMDs start. A $500,000 IRA can lose money converting — the benefit scales with balance size.
Do alternative assets actually improve retirement outcomes? 60,000 Monte Carlo paths on gold, commodities, TIPS & bitcoin
60,000 paths through the same engine as the live calculator test gold, commodities, TIPS, and a small bitcoin sleeve against a standard 5-asset portfolio. TIPS lower success at this withdrawal rate; bitcoin’s headline gain traces back to its assumed return, not diversification.
510,000 retirement Monte Carlo paths across all 51 U.S. jurisdictions: the state-tax cost of retirement in 2026
The same representative retiree (age 60, $2M, 60/40 portfolio, $80K real annual spend) runs through 10,000 Monte Carlo paths in every state plus DC, changing only the state tax code. Wyoming, Louisiana, and South Dakota cluster at the top; California, DC, and New York rank worst.
When does tax-loss harvesting actually pay? NPV across 768 scenarios
Every scenario runs through the same open, unit-tested 2026 federal tax engine as the free calculator, computing exact with-versus-without differences rather than marginal-rate shortcuts. Short-term-gain offsets save 1.71× more than long-term offsets at the top income level tested.
Roth Conversion Breakeven by State (2026)
A traditional→Roth conversion costs the same federal tax everywhere, but the state slice of the bill varies wildly by jurisdiction. This study runs a 1,224-scenario sweep across all 51 U.S. jurisdictions to price the state, federal, and combined cost of converting — and the future tax rate above which converting today wins.
The 4% rule across 123 historical retirement cohorts
A rolling-cohort study of every U.S. retirement start year with a full 30-year window in the Shiller dataset, computing the maximum sustainable withdrawal rate and survival at 4.0/4.5/5.0% for 60/40, 50/50, and 80/20 portfolios. Historical results, not a forecast — a companion to the CME stress test above.
The 2026 IRMAA Cliff Map
Maps every 2026 Medicare IRMAA tier boundary for single and MFJ filers — the surcharge just below vs. at each cliff, the cost of the single dollar that crosses it, and the headroom to the next one. Distinct from and cross-linked with the companion Roth-conversion IRMAA cost study above.
The 2026 OBBBA Senior Deduction, Decomposed
A retiree’s 2026 standard deduction is three deductions stacked together: the base standard deduction, the IRC §63(f) additional deduction for the aged, and the temporary OBBBA §70103 senior deduction. This study decomposes the stack by filing status, age, and MAGI, and maps exactly where the $6,000-per-filer OBBBA piece phases out to zero.
The Optimal Retirement Glide Path (2026)
Should a retiree’s equity allocation glide down, hold flat, or rise? This study hands the whole 5-period schedule to QuantCalc’s optimizer at 3.5% / 4.0% / 4.5% withdrawal rates, then independently re-scores its choice against static 60/40, static 40/60, declining 70→30, and rising 30→70 schedules on common random numbers — reporting a winner only when it beats the sampling noise.
The ACA Bridge Income Plan (2026)
How much income should an early retiree realize — and how much traditional balance to convert to Roth — before Medicare, without crossing the 400% FPL cliff? This study gives six households a recommended year-by-year plan with its per-year coverage regime, against never converting and against a plan that fills the 12% bracket and ignores the cliff.
When Withdrawal Order Helps, and When It Backfires (2026)
Does drawing your accounts in the "tax-smart" order actually cut lifetime taxes? For nine households this study reports the paired per-path median difference, with bands, between a single-year tax-minimizing order and a traditional-first order — and shows the horizon crossover where the benefit inverts into a cost.
Where Retirement Income Is Actually Taxed: the State Pension-Exclusion Map (2026)
Which states exempt or cap pension income versus IRA and 401(k) distributions, at what age, and where the pension SOURCE (government vs private) changes the bill. All 51 jurisdictions grouped by treatment, with the exclusion shown in dollars, computed from the frozen state-tax engine.
Every study ships a seeded, deterministic engine and open data (CSV + JSON) under an open-data license (CC0 or CC BY 4.0, noted on each study). Methods and capital-market assumptions are documented on our methodology page. These studies are educational research, not financial advice.
Want to test these ideas on your own numbers? The free Monte Carlo retirement planner runs in your browser with no signup, and the Social Security claiming-age calculator applies the 2033-reduction analysis to your own benefit.