Applying a single Consumer Price Index (CPI) inflation rate to an entire retirement budget introduces a structural compounding error because retiree expenses do not inflate uniformly across categories. While core living costs—housing, food, utilities, and transportation—historically average 2.5% to 3.0% annual inflation, out-of-pocket medical care, Medigap supplemental premiums, Part D prescription drugs, dental work, and late-life custodial care have historically inflated at 5.5% to 6.5% per year.
Mathematically, modeling total annual expenses as a two-speed sum—Outflow(t) = Core_0(1 + 0.025)^t + Med_0(1 + 0.06)^t—reveals a dramatic budget shift over a 25-year retirement from age 65 to age 90. At 2.5% general inflation, an $82,000 core lifestyle budget multiplies by (1.025)^25 = 1.85×, reaching $152,023 per year at age 90. Over the exact same 25-year span, an $11,500 initial annual healthcare budget compounding at 6.0% multiplies by (1.06)^25 = 4.29×, surging to $49,356 per year—even before factoring in an acute assisted-living or cognitive care event.
What starts at age 65 as a modest 12% line item in the household budget expands to nearly 25% to 30% of total cash outflows by the late eighties. Simultaneously, dedicated Health Savings Account (HSA) balances that appear ample at retirement often exhaust around age 76 to 79 under 6% medical compounding, forcing subsequent medical expenses onto taxable Traditional IRA withdrawals—which in turn inflates MAGI and triggers additional federal income tax on every healthcare dollar spent.
Generic bank calculators miss this divergence completely because they offer only a single blended CPI input, systematically underestimating late-life portfolio depletion.
This template separates core living withdrawals ($82,000 at 2.5% CPI) from dedicated out-of-pocket medical outlays ($11,500/yr starting at age 65 alongside a $65,000 tax-free HSA reserve). Load the preset to inspect when the HSA depletes and how late-life medical expenses impact portfolio survival.