31 lines
1.7 KiB
Markdown
31 lines
1.7 KiB
Markdown
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# FIRE number via Monte-Carlo NW-threshold on the liquid pot
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We compute each Case's target net worth (its "FIRE number") by searching net
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worth for the smallest value at which Guyton-Klinger reaches a 99% Monte-Carlo
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success rate — **not** a fixed safe-withdrawal-rate multiple (e.g. 25× spend).
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A fixed multiple cannot honour the structure the engine already models: the
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rising 30→70 equity glide, per-jurisdiction taxes drained from the portfolio,
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the kids-cost ramp, an optional one-time home purchase, and a workplace pension
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that is locked until ~57. Our block-bootstrap's empirical perpetual SWR is also
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~2.5–3%, materially below the textbook 4%, so a 25× multiple would understate
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the number anyway.
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The solver seeds on **liquid** net worth — it excludes the Fidelity workplace
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pension (inaccessible until ~57) and injects that pension as a grown lump at age
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57. Early-retirement sequence risk is funded only by spendable assets, so seeding
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total net worth would overstate safety exactly where the 99% bar is decided.
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## Consequences
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- A vectorised NW search (binary search over `initial_portfolio`, monotone
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because the GK year-0 draw is an absolute real amount) populates a
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`fire_target` table, one row per (Case × country × with-home).
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- Targets vary by country through **both** COL-scaled spend and the destination
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tax regime (the simulator drains tax from the portfolio since 2026-05).
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- The Grafana countdown reads `fire_target` for the selected country and diffs
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it against current liquid net worth from `account_snapshot`.
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- Pension growth to age 57 is modelled deterministically (current value
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compounded at an assumed real rate), not per-path — a conservative
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simplification, revisitable if it ever binds.
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