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QuantCalc Research

Reproducible retirement studies built on the same engines that power our calculators. Every study documents its assumptions, uses a seeded Monte Carlo or tax engine, and publishes its full results as open data under an open-data license (CC0 or CC BY 4.0, noted on each study).

Studies

If the 2033 reduction happens, the optimal Social Security claiming age moves earlier or stays unchanged — never later — in the base case across 18 profiles.

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.

A 22% Social Security cut drops a balanced retiree’s 30-year success rate from 81.3% to 65.3%.

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 16.0-point fall in success rate for a 60/40 retiree — offset by roughly $118,909 more saved. Run on the planner’s Monte Carlo engine across three allocations and three reliance levels, per the 2026 Trustees Report (ssa.gov/oact/trsum/, checked 2026-09-10).

Crossing the first 2026 IRMAA tier costs $1,148/year single, $2,297/year for a couple.

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.

The 4% rule runs dry on 23% of paths; Guyton-Klinger guardrails cut that to 3.7%.

Withdrawal strategy success rates: guardrails vs. the fixed 4% rule, 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, on the planner engine’s return model. The guardrail plan cuts the 4% rule’s failure rate from 23% to 3.7% — an 84% reduction, by trading depletion for spending cuts — at about 34% less median legacy.

Drawing the IRA first costs early retirees an average $86k–$215k of repaid ACA credit over a 10-year bridge; a better withdrawal order saves $78k–$207k.

The 2026 ACA subsidy cliff for early retirees: an 80,000-path Monte Carlo study

Modeling a 55-to-65 healthcare bridge on the QuantCalc planner’s own return, tax and premium-tax-credit engines, the study measures what the subsidy cliff costs a retiree who does not manage MAGI — and how much a tax-optimized withdrawal order recovers.

Delaying Social Security to 70 beats claiming at 62 in only 42% of lifetimes once the early checks are invested.

Social Security at 70 beats 62 only 42% of the time — if you invest

A 400,000-life Monte Carlo over real mortality (SSA 2022 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.

The same $1M, 4% plan ran out of money in 17.3% of the historical start months whose first decade was in the worst tenth, vs. 0% in the best.

Retiring into a bear market: same plan, 27% failure vs. 0%

Every real 30-year start month since 1926 (819 of them), replayed through the QuantCalc planner’s own engine with the plan held fixed. Retiring in September 1929 ran the money out after about 20 years; the same months in reverse order left $1,735,741.

None of six published Capital Market Expectations reproduce the 4% rule’s near-100% historical safety; five land between 69% and 86% over 30 years, and one mean-reverting forecast collapses it to 5.6%.

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 an 89.5% historical baseline every forecast lands lower, and among the survivors median terminal balance spans nearly 3× — a plan’s safety margin depends heavily on which return assumption it borrows.

A married couple with a $1M Traditional IRA that skips gap-year Roth conversions pays a median $38,224 more in lifetime federal income tax; at $2M, $146,598 more.

The lifetime tax cost of skipping Roth conversions in the gap years

A year-by-year federal income tax simulation, every year priced by QuantCalc’s federal tax engine on 2026 law, compares doing nothing with a Traditional IRA against filling the 12% bracket with Roth conversions before RMDs start at 75. Converting wins in 62.5% of return paths at $500,000 and 92.6% at $2M — the benefit scales with balance size.

At a stressed 5.5% withdrawal rate, a diversified 20% alternative-asset sleeve lifts 35-year success +6.86 points and rescues the bottom-quartile retiree from a depleted balance to $107,152.

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.

One couple, 51 jurisdictions: a median $162,597 of income tax and IRMAA over 30 years where their state charges nothing, $309,718 in Oregon.

510,000 retirement Monte Carlo paths across all 51 U.S. jurisdictions: the state-tax cost of retirement in 2026

The same couple (both 60, $2M, 60/40, $80,000 a year to spend after tax) runs through QuantCalc's tax-aware planner 10,000 times in every state plus DC, changing only the state. 16 jurisdictions tie for the lowest tax; Oregon, Maryland and Massachusetts cost the most.

Harvesting a $10,000 loss produces a positive net present value in 78.4% of 768 tested scenarios — but 0%-bracket harvests always lose, up to $1,865.

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.

Converting the same $50,000 IRA balance costs $4,375 in Oregon state tax alone — and $0 in the 13 states that don’t tax the conversion at all.

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.

Across 123 historical U.S. retirement cohorts (1871–1993), a 60/40 retiree’s maximum sustainable 30-year withdrawal rate ranged from 3.69% (the unluckiest, 1966) to 10.64%, median 6.15%.

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 (ie_data.xls, checked 2026-09-10), 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 largest single 2026 IRMAA cliff costs $1,736 per person the moment income crosses it — 51% more than the first cliff’s $1,148, with the top tier reaching $6,936 per person a year.

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.

A single filer turning 65 in 2026 stacks $8,050 in extra deductions below $75,000 MAGI (an MFJ couple both 65+ stacks $15,300 below $150,000) — and loses the $6,000 OBBBA piece entirely by $175,000 single / $250,000 MFJ.

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.

Under QuantCalc’s forward-looking model, the optimal 5-period glide-path shape depends on the withdrawal rate — the optimizer ties or beats every preset schedule, its edge over static 60/40 growing from +0.4 pp at 3.5% to +5.5 pp at 4.5%.

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.

In 2026 the ACA subsidy cliff is back above 400% FPL. Across six early-retiree households, a plan that ignores the cliff costs $65k–$234k more over a three-to-five-year bridge than the recommended year-by-year income and conversion plan that holds the premium subsidy.

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.

Which withdrawal order actually saves the most lifetime tax — and can it change whether the money lasts? Spending is after tax: each year's withdrawal funds spending plus that year's tax bill, debited from the accounts drawn. QuantCalc now searches whole-retirement withdrawal orders (plus Roth-conversion candidates) per household; for a pre-RMD corridor household the recommended order saves a paired median of $16,836 (present value) against drawing traditional first, while the old single-year "lowest tax this year" rule alone would cost a high-balance (IRMAA-exposed) household a paired median of $52,157 more than traditional-first. Nine households, recommended order per household with its portfolio survival against traditional-first, free CSV/JSON.

When Withdrawal Order Helps, and When It Backfires (2026)

Which order saves the most lifetime tax, household by household? For nine households this study names the recommended whole-retirement order and its paired per-path present-value saving against traditional-first, reports what the single-year lowest-tax order would have cost or saved beside it, and shows a horizon sweep where the single-year order's benefit inverts into a cost.

Across the 51 U.S. tax jurisdictions in 2026, 7 states tax the SAME retirement income differently by source: Alabama makes a $75,000 employer pension state-tax-free but charges $3,185 on the same amount drawn from an IRA, and Missouri exempts a $75,000 government pension down to $286 while taxing a private pension or IRA at $2,588.

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.

Filling the 22% bracket costs 20.9% of the amount converted, so at a 22%+ final rate the conversion is ahead from year one at every age — but against a 12% final rate at 6% growth the crossover must be earned: a 13-year wait converting at 75, 19 years at 65, 26 years at 55, with the SECURE 2.0 RMD age (73 vs 75) setting the pace.

Roth Conversion Breakeven by Age (2026)

When does paying Roth-conversion tax now overtake deferring, and how does the answer move with the converter's age? 756 deterministic scenarios across conversion ages 55–75, three bracket targets, three growth rates, and four final marginal rates — with the SECURE 2.0 RMD seam (73 vs 75) and the IRMAA lookback computed from the same parity-tested engine as the by-state companion study.

One full 12-month period of Part B delay adds $20.29/month permanently in 2026; a five-year dual gap runs $124.85/month — $29,964 held flat to age 90 — and after ten years the Part B penalty reaches 100% of the standard premium itself.

The Cost of Delaying Medicare Enrollment (2026)

What does delaying Medicare enrollment actually cost? The permanent Part B penalty (10% of the $202.90 standard premium per full 12-month period) and Part D penalty (1% of the $38.99 national base premium per uncovered month) computed for every delay from 0 to 120 months and priced into lifetime cost streams at ages 85, 90, 95 and an IRS life-expectancy horizon — with the creditable-coverage paths that make a delay free, and the COBRA seam that does not.

Inside the Social Security taxability phase-in a “tax-free” muni dollar carries a 18.7¢ federal rate in the 22% bracket — $10,000 of muni interest costs a single retiree with $36,000 of benefits $1,094 of federal tax — and past the window the same dollar can still cross an IRMAA floor ($1,148.40/yr per person) or the ACA cliff ($12,697 on one dollar).

Municipal Bond Interest and the Social Security Tax Torpedo (2026)

Municipal-bond interest is federal-tax-free as income but counts in three statutory income tests: Social Security provisional income (IRC §86(b)(2)(B)), IRMAA MAGI and ACA MAGI. 984 scenarios across both filing statuses, three benefit levels, an income sweep and four muni levels compute the muni dollar's four regimes (0 → 0.50× → 0.85× bracket → 0 at the ceiling), the torpedo-window edges, the IRMAA tier jumps and the 400% FPL cliff — through the same engine as the live torpedo calculator.

On the same $72,000 of income, a surviving spouse filing single owes 4.1× the federal tax of a joint return ($1,155.00 → $4,780.00); at $170,000 the filing-status change alone adds $12,020.00 (+78%) plus the survivor's first IRMAA surcharge of $2,884.80/yr.

The Widow's Penalty: the Survivor Filing-Status Change (2026)

When one spouse dies, the survivor keeps most of the income — the larger Social Security check, the pension, the RMDs — but files single after the year of death (IRC §6013(a)(3); the §2(a) qualifying-surviving-spouse extension requires a dependent child and rarely applies to retirees). 488 scenarios compute the before/after: the standard deduction and bracket edges halve, IRMAA thresholds halve (42 U.S.C. §1395r(i)(2)(B)), the §86(c) thresholds drop, and each household's change is decomposed into a filing-status penalty and an income effect — through the same engine as the live widowhood calculator.

A $25,000 gift from a $2M IRA at 73 cuts the single filer's federal tax to $5,358.60 as a QCD vs $10,546.28 as a cash gift under the standard deduction — $216.31 vs $8.80 saved per $1,000 given; at 80 the same QCD also erases a $1,148.40/yr IRMAA surcharge a cash gift cannot touch.

Qualified Charitable Distributions: the AGI Exclusion vs the Charitable Deduction (2026)

A retiree 70½+ can give the same dollars three ways: a qualified charitable distribution straight from the IRA (excluded from AGI under IRC §408(d)(8), counts toward the RMD, $111,000/person in 2026 per Notice 2025-67), a cash gift under the standard deduction (relieved only by the new §170(p) $1,000/$2,000 non-itemizer deduction), or an itemized cash gift under the new 0.5%-of-AGI floor. 792 scenarios compute all three — federal tax, §86 Social Security taxability, IRMAA tiers, tax saved per $1,000 given — through the same engine as the live QCD calculator; the AGI-exclusion-vs-deduction seam does all the work.

At an illustrative 2.0% real yield a 30-year TIPS ladder pays $44,650 per $1M and $895,858 locks in $40,000 real for 30 years on every market path ($960,634 at 1.5%, $837,212 at 2.5%) — while the quoted 4% rule on the same $1M runs out in 14.1%–31.4% of paths under five forecasts yet leaves a median $264,366–$781,070 at year 30.

TIPS Ladder vs the 4 Percent Rule: Locked-In Real Income or Market Upside for 30 Years (2026)

Which is safer for a 30-year retirement, a TIPS ladder or the 4% rule? This study prices a 30-year ladder at three illustrative real yields — income per $1M, cost per $1 of real income, the capital that locks $40,000 real for 30 years and the residual left for equities — and sets it beside the 4% rule’s failure share and terminal wealth quoted, not re-simulated, from QuantCalc’s published forward-looking, sequence-of-returns and historical-cohort studies. A hybrid row puts essentials on the ladder and the rest at market; the two failure modes are spelled out in plain words.

At an illustrative 6.5% payout a life-only immediate annuity turns $1M into $65,000 a year for life on every market path and every lifespan — worth $40,659 real by year 20 and $31,763 by year 30 at 2.5% inflation, with nothing left at death; 45.9% of 65-year-old men and 58.1% of women reach the age-84 real break-even — while the quoted 4% rule on the same $1M keeps its income inflation-adjusted and a median $264,366–$781,070 at year 30 yet runs out in 14.1%–31.4% of paths under five forecasts.

Annuity or the 4 Percent Rule: Which Gives More Secure Retirement Income? (2026)

Annuity or the 4% rule — which gives more secure retirement income? This study prices a life-only immediate annuity bought at 65 at three illustrative payout rates — income per $1M, its real value in years 10, 20 and 30, the premium that covers $40,000 of first-year spending, the break-even age and an annuitise-the-essentials hybrid — reads survival to 80/85/90/95 from the SSA period life table (checked 2026-09-10) behind the site’s claiming research, and sets it all beside the 4% rule’s failure share and terminal wealth quoted, not re-simulated, from QuantCalc’s published Monte Carlo studies. Longevity and sequence risk on one side, inflation, liquidity and bequest on the other, in plain words.

A 3-year cash bucket on a $1M, $40,000-a-year, 60/40 retirement reached 95 with money left in 84.5% of 10,000 paths against 86.0% for a total-return portfolio holding the same starting cash — and on the same market paths ended $12,210 more at the median, finishing higher in 58.2% of paths. Across 36 cells the bucket ran out more often in every one (−0.6 pp to −5.3 pp) while its paired median ran from $0 to +$29,739: a better middle, a worse tail.

Bucket Strategy vs Total Return: Does a Cash Bucket Protect a Retirement Portfolio? (2026)

Bucket strategy or total return — does a cash bucket protect a retirement portfolio? This study runs the engine’s two-bucket rule (2, 3 and 5 years of spending in cash, refilled after non-losing years or when below half) against a total-return portfolio built to hold the same starting cash, for 3.5%, 4% and 4.5% spending on 60/40 and 80/20 plans, 10,000 paired paths per arm. Success rates, median and 10th-percentile wealth at 95, and the per-path paired difference — median, band, share of paths the bucket ends higher, survival crossovers — with the gap followed year by year and the refill rules compared head to head.

For a couple both 62 with $1M on 60/40 spending $60,000 a year to 95 (PIAs $3,000 / $1,500), the lower earner claiming at 62 and the higher at 70 ended $3,325 more at 95 than both at 67 on the same 10,000 paths, higher in 52.9% of them — and +$106,120 once the higher earner dies at 80 and the survivor keeps $3,720 a month instead of $3,000. Nine combinations ran from −$205,926 to +$101,889 at the median; success stayed between 90.1% and 100.0%.

Should the Lower Earner Claim Social Security Early and the Higher Earner Delay? A Household Monte Carlo (2026)

Should the lower earner claim Social Security early and the higher earner delay? This study runs every combination of 62, 67 and 70 for both spouses through the engine’s household model on identical market paths — two benefit personas ($3,000 / $1,500 and $2,500 / $800 at full retirement age), 10,000 paired paths per arm, with and without the higher earner dying at 80 — and reports success, wealth at 95, the per-path difference against claiming together at 67, the lifetime benefits each combination pays and what the survivor keeps, with the gap followed year by year.

For a 60-year-old with $800,000 on 60/40, saving $30,000 a year and spending $60,000 with $30,000 of Social Security from 67, retiring at 66 instead of 65 lifted success to 95 from 96.5% to 98.1% on the same 10,000 paths — +1.6 pp for one year, against +1.1 pp for saving $10,000 a year more for five years and +2.3 pp for spending $5,000 a year less. In a marginal plan ($600,000, $67,000 a year, baseline 70.5%) the same three moves were worth +10.5 pp, +6.0 pp and +12.2 pp.

Work One More Year or Save More: Which Moves Retirement Success More? (2026)

Work one more year or save more — which moves retirement success more? This study runs six arms against a retire-at-65 baseline on identical market paths: retire at 66 or 67, save $10,000 or $20,000 a year more for the last five working years, or spend $5,000 or $10,000 a year less — for a comfortable and a marginal persona, 10,000 paired paths per arm. Success rates, median and 10th-percentile wealth at 95, the per-path paired difference, and success gained per year worked, per $10,000 saved and per $5,000 cut, with the gap followed year by year and the mechanism spelled out in plain words.

Retiring at 55 with $1.2M on 70/30, spending $55,000 a year to 95 with $28,000 of Social Security from 67, five years of $10,000 a year raised success from 88.3% to 90.4% and ended $212,210 more at 95 at the paired median on the same 10,000 paths; ten years, 92.5%. The tight $950,000 plan went from 66.8% to 72.5% and 77.3%. Earned over five years vs the same $50,000 saved at 55: a higher success rate (90.4% against 90.3%) and $17,934 less at the median.

Part-Time Income in Early Retirement: How Much Does $10,000 a Year Change the Plan? (2026)

How much does $10,000 a year of part-time income change an early-retirement plan? This study runs $10,000, $20,000 and $30,000 a year for five and ten years from 55 through the engine on identical market paths — a plan that mostly works and a tight one, 10,000 paired paths per arm — and reports success, wealth at 95, the per-path difference against not working, success gained per $10,000-year, the gap followed year by year, and the same money saved beforehand instead of earned.

For a single filer with $80,000 of other income inheriting $300,000, a year-1 lump sum pays $87,364 of federal tax on the IRA dollars (29.1% of the inheritance, into the 35% bracket), a level ten-year draw $81,403, filling the 22% bracket $78,876, and nothing until year 10 $145,254; at $600,000 against $160,000 the lump sum costs $204,066 versus $190,508 level — and for a beneficiary of 64, the level draw pays $11,484 of IRMAA over ten premium years against the lump sum’s single $6,355.

Inherited IRA Under the 10-Year Rule: Spread the Withdrawals or Take a Lump Sum? (2026)

Inherited IRA under the 10-year rule — spread the withdrawals or take a lump sum? This study empties $300,000 and $600,000 inherited traditional IRAs six ways inside the SECURE Act window — lump sum, 1/N of the balance, level draw, fill the current bracket, annual RMD then year 10, nothing until year 10 — against $80,000 and $160,000 of other income, at 5% and 3% growth, through the same 2026 federal-tax, IRMAA and Single-Life-Table modules the site’s calculators run. Tax on the IRA dollars, share of the inheritance, effective rate, highest bracket reached, after-tax value nominal and discounted, and an IRMAA sub-case for a beneficiary already near Medicare, with the bracket mechanics spelled out in plain words.

Paying off a $200,000, 5.5% mortgage at 65 from a $1M, 60/40 portfolio with $50,000 a year of other spending reached 95 with money left in 31.2% of 10,000 paths against 34.3% for keeping the loan and investing — and on the same market paths keeping it ended higher in 34.1% and lower in 0.3%, a mean difference of +$74,916. A simulated break-even exists only where the plan has room: 4.06% nominal at 5.5% / $30,000, 6.11% at 6.5% / $30,000; across the 2 cells with a tie in range it sits −1.44 pp to −0.39 pp from the rate itself.

Pay Off the Mortgage or Invest Before Retirement? Paired Monte Carlo Results (2026)

Pay off the mortgage or keep investing before retirement? This study runs the two choices on identical market paths for a 65-to-95 retiree with $1,000,000: a $200,000 balance with 15 years left at 4.0%, 5.5% and 6.5%, the level payment charged as a nominal constant, and $50,000, $40,000 or $30,000 a year of other spending, 10,000 paired paths per arm. Success rates, median and 10th-percentile wealth at 95, the per-path paired difference — median, mean, band, share of paths each arm ends higher, survival crossovers — followed year by year, and the break-even portfolio return found by re-running every cell across a grid of return shifts.

On identical market paths for a $1M, $40,000-a-year, 60/40 retirement, guardrails reached 95 in 99.7% of 10,000 paths (99.2% of the worst-decile first decades) by cutting the median worst-decile path to $26,585 a year; a bond tent lifted success from 86.0% to 87.6%–86.8% (23.7% to 33.7%–34.4% in the worst decile) at a lower median; a 3-year cash bucket reached 84.5% against 86.0% for the same cash held in a level-spending portfolio.

Bond Tent, Cash Bucket or Guardrails: Which Handles Sequence-of-Returns Risk Best? (2026)

Bond tent, cash bucket or guardrails — which handles sequence-of-returns risk best? This study runs a rising-equity glide path (40% equity at 65 to 60% or 70% by 75), the engine’s two-bucket cash reserve (3 and 5 years, with matched-cash controls) and Guyton-Klinger guardrails against a constant 60/40 level-spending control on the same 10,000 paths, for 3.5%, 4% and 4.5% spending. Success, wealth at 95, the per-path paired difference, realised spending path by path, and every figure cut by decile of first-decade return — with what each defence changes and what it costs in plain words.

On one $1,000,000 plan spending $40,000 a year to 95, applying each published forecast over its own horizon instead of stretching it across 30 years moved success by +0.4 pts for a 20-year forecast, +5.1–7.2 points for the ten-year forecasts, and +40.7 pts for the 7-year one — 5.0% against 45.7%.

Your 30-Year Plan Is Built on a 7-Year Forecast: What the Horizon Mismatch Costs (2026)

Capital market assumptions are published over 7, 10, 20 and 30 years; retirement plans run 30. This study runs one plan 5 ways twice on 10,000 paths per arm — each forecast stretched across all 30 years, then applied only for the years its publisher forecasts with a 30-year set thereafter — and reports what the difference is worth in success rate and terminal wealth. It is the general form of a correction to our own 4% rule stress test.

The same retirement income, priced in every state: how much the state, not the income, decides.

Same Retirement Income, 51 Different State Tax Bills: Ten Retiree Households Priced in Every State (2026)

Ten retiree households — Social Security with IRA withdrawals or a private pension, single and married — priced for 2026 in all 50 states and DC by the open federal and state tax engines. Federal tax is the same everywhere; the state column runs from nothing to thousands of dollars. Every row is replayed through the public tax APIs.

What a Roth conversion adds to the 2026 return in each state, and where it adds nothing.

The Tax on a $25k, $50k or $100k Roth Conversion in Every State (2026)

The extra federal and state tax a $25,000, $50,000 or $100,000 Roth conversion adds to a retiree’s 2026 return, for a single filer and a married couple, in all 51 jurisdictions — including the Social Security that becomes taxable, the senior deduction that phases out, and the effect on the 2028 IRMAA surcharge.

Under the 2026 charitable rules, which way of giving the same dollars saves the most.

Cash, DAF Bunching, Appreciated Stock or QCD: What Each Gift Saves Under the 2026 Rules

Three retiree households give the same amount each year for three years: cash every year, three years bunched into a donor-advised fund, appreciated stock, or a qualified charitable distribution. Federal tax and IRMAA are computed under the 2026 rules: the AGI floor on itemized gifts and the new deduction for people who do not itemize.

Why tax withheld in December can do what a January estimate cannot.

Pay a Q4 Estimate or Withhold From an IRA in December? The 2026 Underpayment Penalty, Computed

Two retirees whose 2026 tax jumped late in the year close the same shortfall three ways — nothing until April, a fourth-quarter estimate by January 15, or withholding from a December IRA distribution — and the Form 2210 penalty of each is computed on the 2026 installment calendar and the announced IRS rates.

When a gain taxed at 0% still raises the tax bill, and when it costs more than the gain.

Is 0% Capital-Gains Harvesting Really Free? Not With Social Security, the ACA or IRMAA (2026)

Harvesting long-term gains inside the 0% bracket is a standard year-end move. For retirees it is often not free: the gain can make more Social Security taxable, shrink the senior deduction, cut the ACA premium credit or cross an IRMAA tier. Each case is computed with and without the harvest.

Seven year-end moves, twelve retiree households, four lines of the bill at once.

Which Year-End Move Cuts a Retiree's 2026 Tax Most? 7 Moves x 12 Households, Federal + State + IRMAA + ACA

A Roth conversion, loss and gain harvesting, bunching, a QCD, the last RMD and the fourth-quarter payment, each run for twelve illustrative households at three sizes: the change in federal tax, state tax, the IRMAA surcharge 2026 income sets for 2028 and the ACA credit, and what the moves do together compared with alone.

Where the same QCD or conversion is worth more, and where the state takes nothing.

The Same Year-End Move Is Worth Different Amounts in Each State: QCD and Roth Conversion, 51 Jurisdictions (2026)

A qualified charitable distribution in place of a cash gift and a Roth conversion, priced for two retiree households in all 50 states and DC: the federal change is the same everywhere, the state line is not.

What $12,000 to $48,000 of rent adds on top of retirement income, and what a rental loss saves.

How Much Tax Does Rental Income Add in Retirement? Federal and Every State, 2026

Four retiree households priced with and without net rental income in all 50 states and DC: the federal tax it adds (including the Social Security it makes taxable and the 3.8% NIIT), the state tax it adds, and the passive-loss allowance on a rental loss.

Three credits open to retirees on paper, and how few households can use them.

Which Tax Credits Can a Retiree Claim in 2026? EIC, Saver's Credit and the Credit for the Elderly, Computed

The earned income credit, the saver's credit and the credit for the elderly or disabled computed for early retirees working part time, pensioners over 65 and people retired on disability: who qualifies, who can use the credit, and the rules that shut retirees out.

The part-year tax in every state a retired couple might leave, and the timing of a Roth conversion.

Moving to Another State in Retirement: What the State You Leave Still Taxes, and When to Convert (2026)

A retired couple moving to a state with no income tax on July 1: the old state's part-year tax, the saving from converting to Roth after the move, how each state taxes the couple when one spouse moves first, and five moves between income-tax states.

Which of 4,398 local income taxes reach Social Security, IRA and pension income.

Local Income Tax on Retirement Income: Every County, City and School District, 2026

Every county, city, school district and municipality in the local-tax registry, priced for a retired couple, a working couple and a higher-income retired couple: the earned-income taxes reach none of the retirement income; the taxes on state taxable income do.

Five retiree households, 255 complete 2026 returns, federal and state.

2026 Tax Return for Retirees, Every State: Refund or Amount Owed for Five Typical Households

What five typical retiree households owe, or get back, on their 2026 federal and state returns in all 50 states and DC, with 10% withheld from IRA withdrawals and pensions: AGI, taxable Social Security, the new senior deduction, the tax and the balance at filing.

64 retiree cases and 204 state returns: the tax a 2026 RMD really adds.

How Much Tax Will You Pay on Your RMD? 2026 Required Minimum Distributions From $250,000 to $2 Million, Federal and Every State

The federal tax a 2026 required minimum distribution adds for four retiree households at ages 73 to 85 and IRA balances of $250,000 to $2 million, why it often runs above the bracket (the Social Security it makes taxable, the senior deduction it phases out), the IRMAA effect, and the state tax on the same RMD in all 50 states and DC.

24 withdrawals, six households: the 20% withheld against the real tax.

How Much Tax Do You Pay on a 401(k) Withdrawal in 2026? The Real Tax vs the 20% Withheld, Six Households and Every State

The federal tax a $10,000 to $100,000 401(k) withdrawal adds in 2026 for working, early-retired, rule-of-55 and retired households, the 10% additional tax, whether the plan’s 20% withholding covers it, the withdrawal that nets $25,000, and the state tax in every state.

30 households, 102 state ceilings: the most income a retiree can have at $0 tax.

How Much Income Can a Retiree Have and Pay No Federal Income Tax in 2026? The $0-Tax Ceiling by Household and Social Security, and Every State

The most IRA or pension income, and the most long-term capital gains, a retiree can have in 2026 with $0 of federal income tax, for single filers and couples at 62 and 65+ with $0 to $60,000 of Social Security, and where each state starts taxing the same income.

63 workers, 12 in the year of full retirement age, 51 state returns: the earnings test and the recredit.

Working While Claiming Social Security in 2026: What the Earnings Test Withholds, What You Keep, and When You Get It Back

How much Social Security the 2026 earnings test withholds from a worker under full retirement age who earns $20,000 to $100,000, for claim ages 62 to 65 and three benefit levels; what is left of the paycheck after the withholding, payroll tax and federal income tax; and how many years the recredit at full retirement age takes to pay the withholding back.

12 tier cliffs, 6 households, 22 moves: the surcharge on the crossing dollar against its income tax.

IRMAA Cliffs in 2026: What $1 Over Costs Against the Income Tax on It, and the Moves That Push Retirees Over

What one dollar over each 2026 IRMAA tier adds in Part B and Part D surcharges for single, joint and separate filers, against the federal income tax on that income, and which common moves (a Roth conversion, a long-term gain, the year’s RMD) push six typical retiree households over a tier.

12 federal cases and 600 federal-plus-state cases: pretax now vs tax later on the 2026 catch-up.

Catch-Up Contributions in 2026: What the 60–63 Super Catch-Up and the Roth Catch-Up Rule Are Worth, Six Households and Every State

The tax a pretax 2026 catch-up saves now against the tax on the same dollars at 75, for six households earning $90,000 to $250,000 at 55 and 61, what the $11,250 super catch-up for ages 60–63 adds, and what the rule that catch-ups be Roth above $150,000 of FICA wages costs, federal and in every state but Pennsylvania.

Splitting a big withdrawal across December and January is not always cheaper.

Split a Large IRA Withdrawal Across Two Tax Years or Take It at Once? Federal, Every State and IRMAA (2026)

Four retiree households take $30,000 to $200,000 from an IRA in one tax year or half in each of two: the federal tax, the IRMAA surcharge and the state tax in all 50 states and DC. Splitting usually saves, but where Social Security is partly taxable it can cost more.

Two single returns or one joint return: what marrying changes for retirees.

Does Getting Married in Retirement Raise Your Taxes? Eight Retiree Couples, Federal, IRMAA and Every State (2026)

Eight pairs of retirees priced unmarried and married for 2026: federal income tax, the Medicare IRMAA surcharge and the state tax in every state, and the three joint-return rules behind a penalty.

Pretax or Roth, by where you work and where you retire.

Roth or Traditional 401(k)? The Answer by State, and What Retiring to a No-Tax State Changes (2026)

The tax a $10,000 traditional 401(k) contribution saves in 2026 against the tax on the same dollars at 75, for six households earning $60,000 to $250,000, in every state but Pennsylvania: staying put, retiring to a no-income-tax state, or the reverse.

Taxable is not the same as taxed.

Is Social Security Taxable in 2026? How Much of the Benefit Is Taxed, and the Federal Tax It Adds, for 36 Retirees

Thirty-six retirees, single and married, with $20,000 to $60,000 of Social Security and $0 to $160,000 of IRA withdrawals: the share of each benefit that is taxable on the 2026 federal rules, the federal tax the benefits add, and how many owe $0 with the senior deduction.

Exempt is not always the end of it.

Which States Tax Social Security in 2026? The State Tax the Same Benefits Add, in All 50 States and DC

The same 36 retirees priced in every state with and without their benefits: the states whose rules tax Social Security, and the states that exempt it where the benefits still raise, or lower, the state tax.

The same dollars, five kinds of income, 51 state answers.

Which States Tax Retirement Income in 2026? Pension, IRA, 401(k), Capital Gains and Interest, Priced in Every State

Four retirees on Social Security add $20,000 to $100,000 as a pension, an IRA or 401(k) withdrawal, long-term gains or interest: the state tax each adds in every state, and the states that tax none of it.

The same pay, exempt in one state, taxed like any pension in the next.

Which States Tax Military Retirement Pay in 2026? Four Military Retirees Priced in Every State

Four military retirees, from a 45-year-old with a second career to a couple at 67: the state tax their military retirement pay adds in all 50 states and DC, what each state's military rule saves against a private pension, and the best states for military retirees.

Same income, same withholding: what the 2026 law changes do to the refund.

Will Your 2026 Tax Refund Be Bigger? The Same Household's 2025 and 2026 Tax, Federal and Every State

Nine households priced on their 2025 and 2026 returns with the same income: the federal refund change from the 2026 inflation adjustments, why the senior, tips and overtime deductions do not make 2026 bigger, and the state tax changes in all 50 states and DC.

A capital gain costs more than its own rate.

Capital Gains Tax by State for Retirees (2026): The Federal, IRMAA and State Tax on Selling $25,000 to $500,000 of Stock

Three retirees sell stock for a $25,000 to $500,000 long-term gain: the federal tax with the NIIT and the Social Security it makes taxable, the IRMAA surcharge, and the state tax in all 50 states and DC.

The ranking moves with the income.

State Income Tax on Retirement Income by State and Income Level (2026): $40,000 to $300,000, All 51 Jurisdictions

Two retirees on Social Security and IRA withdrawals at six income levels, $40,000 to $300,000: the 2026 state income tax and effective rate in all 50 states and DC, and the states that leave a modest income untaxed but tax a large one.

Ten withdrawals can use ten exclusions.

Inherited IRA Tax by State (2026): a Lump Sum or Ten Years of Withdrawals, Federal and All 51 Jurisdictions

Three beneficiaries inherit a $300,000 or $500,000 IRA: the federal tax, IRMAA and the state tax in every state if they take it at once or over the ten years of the 10-year rule.

The bracket is not the rate.

Your Tax Bracket in Retirement vs the Rate on Your Next IRA Dollar (2026): Four Retirees, Federal and Every State

Four retirees at 67 take $0 to $150,000 from an IRA: the 2026 bracket they reach against the federal tax on the next $1,000, and the combined federal and state rate in every state.

A 60-year-old’s 2027 benchmark averages $1,489 a month in the HealthCare.gov states; a dollar over 400% of the poverty line costs $11,339 of credit.

2027 ACA Benchmark Premiums and Subsidies for Early Retirees, by State and Age (50 to 64)

The benchmark (second-lowest-cost silver) premium at ages 50 to 64 for one adult and a couple, in 29 states and every county CMS covers, with the 2027 premium tax credit from 150% to 400% of the poverty line, the cliff a dollar above it and the net premium. From CMS’s public use files; CSV and JSON included.

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 needs no signup, and the Social Security claiming-age calculator applies the 2033-reduction analysis to your own benefit.