BucketSavers

How the math works

Order of operations

Each year: withdraw from Bucket 1 (reaching further down the chain if it's dry) → cascade-refill each front bucket back to its target, front to back → apply each bucket's return. Refilling before growth means transferred money earns the destination bucket's lower return that year — a slightly conservative choice, made deliberately.

The refill rule

Each front bucket has a target measured in years of spending, re-priced to the current year's withdrawal so targets rise with inflation. In normal years the cascade tops every front bucket back to target. During a downturn the cascade pauses: Bucket 1 keeps refilling from Bucket 2, but nothing behind Bucket 2 is sold — the growth buckets ride the event out. If the downturn outlasts your front buckets, withdrawals reach into the growth buckets in order — Bucket 1, then 2, then 3, and so on — a forced sale at depressed prices, shown, not smoothed over.

Coming out of a downturn your front buckets are drained, and how you rebuild them turns out to matter more than almost anything else. Refilling them to target in a single year means liquidating years of spending out of stocks in one January — which nobody actually does. With Rebuild the buffer gradually on, each bucket behind Bucket 1 replaces what it handed forward plus one extra year of spending, so a four-year bucket takes four years to come back. Bucket 1 is never throttled; it holds the money you live on this year. Switch the rule off and watch what the lump-sum refill costs — with small front buckets it is a rounding error, but at eight or thirteen years of buffer it is the difference between a plan that works and one that doesn't.

What the downturn does

You set three things: how far the market drops, how long it stays down, and which year it starts. The drop is applied once, then the market holds flat for the full length — struck assets earn nothing until the window ends, at which point normal returns resume from wherever the balances landed. There is deliberately no recovery leg: the shape and timing of a rebound is a forecast, and inventing one would be exactly the kind of false precision this tool avoids. Each bucket's share of the drop is scaled by where its return slider sits between your lowest and highest bucket — the slider stands in for equity exposure, so Bucket 1 doesn't move and the reservoir takes nearly the whole hit. A flat, un-recovering downturn is a pessimistic scenario on purpose; real crashes usually do recover eventually, and a retiree who wants to model that can shorten the "stays down" figure to represent the depth at a chosen point in time.

The comparison lines

Every line spends the same dollars on the same schedule through the same downturn; tap any to show or hide it.

Safe, Moderate, Growth are buy-and-hold blends — 30%, 60%, and 85% in growth, the rest in cash — built from the two rates you already set (cash = Bucket 1, growth = Reservoir). They're bought once and never rebalanced, and each year's withdrawal is taken proportionally from both sleeves so the mix stays put. This is what "just leave it in a balanced fund and don't touch it" actually does. Note that the blend's cash portion isn't protected the way Bucket 1 is — it only dilutes the blended return. Same asset, different job: your Bucket 1 cash is ring-fenced and spent first, so it shields income; the blend's cash just averages the pain. The Growth blend, 85% exposed, craters in a crash nearly as hard as being all-in on stocks.

Rebalanced 60/40 holds a fixed 60% growth / 40% cash mix (built from your Reservoir and Bucket-1 rates) and rebalances to it every year — buying stocks all the way down and trimming them on the way up. It's fixed on purpose: it does not follow your bucket sizing, so when you resize your front buckets you watch the bucket line move against a benchmark that stays put. Expect it to finish low here, and understand why before you draw a conclusion from it: rebalancing's payoff is buying cheap shares that later become dear, and this model's downturn has no rebound to collect on. What's left is the other half of the mechanism — trimming your fastest-compounding asset every year to buy your slowest — which over thirty years is expensive. Compare it to the Moderate line, which holds the same mix and never rebalances: the gap between them is the price of rebalancing in a market that doesn't bounce. If you believe crashes recover, this line is understated. It's the least intuitive benchmark and the one whose result you should question hardest, so it gets its own page.

How big should the front buckets be?

Bigger is not safer. Cash has historically earned almost nothing after inflation — US T-bills returned about 0.3% real over the last century — so every year of spending you park in the front is a year not compounding, and against withdrawals that rise with inflation, that bleeds. A large buffer also takes longer to rebuild after a downturn, which is its own drag. Size the front buckets to the length of the downturn you actually want to sit through, and understand that each extra year of cushion is bought with real money. The tool will show you the price; it won't pick a number for you.

A drift worth knowing about

Because your front-bucket targets grow only with inflation while the reservoir moves at its own rate, the strategy's mix between safe and growth assets shifts over time on its own — no glidepath knob required, and none offered, because adding one would just fight the rule already in place. Which way it drifts depends on you: if your growth outruns your withdrawals, equity share rises with age; if withdrawals are eating into your wealth — the more common case — it falls. Either way it's a consequence you can watch in the year-by-year table, and steer by changing your bucket targets.

What this tool is not

No taxes (planned for a later phase — assets are treated as one pool), no Monte Carlo success percentage, no verdict badge. A success probability is a green checkmark that hides its own machinery; a downturn you place on the timeline — depth, length, and start year all yours — is something you can interrogate. Everything here is in nominal dollars: returns as people quote them, withdrawals escalated by your inflation number where the scheme calls for it. One honest caveat about the comparison: which line wins depends heavily on assumptions this model makes explicit rather than hides. A permanently repriced market flatters cash-heavy strategies and punishes rebalancing; a market that rebounds does the reverse. Read the lines as a map of consequences under your assumptions, not as a verdict. What they buy isn't the highest ending balance; it's income that never depends on selling something that just dropped, and a plan you can actually stick to when the screen is red. This tool exists to show you that trade with the price tag attached, not to talk you into either side.

Glossary

Reservoir

The last bucket. It has no target and is never refilled — it's the growth engine that feeds the chain, and the only bucket you never take income from directly.

4% rule (Bengen)

Withdraw 4% of your starting assets in year one, then give yourself a raise for inflation each year regardless of what markets do. Fixed income; can deplete.

% of current balance

Withdraw a fixed percentage of whatever the portfolio is worth that year. Income swings with markets; mathematically never fully depletes.

Sequence-of-returns risk

Why a downturn's start year matters more than its depth: the same drop early in retirement, while withdrawals are eating a shrunken portfolio, does far more damage than the identical drop fifteen years in.

Rebalancing

Periodically selling whatever grew past its target weight and buying whatever fell below it, to restore a fixed mix. It mechanically buys low and sells high — but demands you buy stocks during a crash.

.buk file

Your plan saved as a plain JSON file on your device. Load it later to pick up where you left off. Nothing is ever sent anywhere.