The 4% rule's valuation trap: why the safe number isn't safe right now

Here’s a confession that should bother you: the most quoted number in early retirement has a variable in it that nobody ever fills in. The 4% rule tells you to save 25 times your annual spending, retire, and draw 4% a year rising with inflation. What it never asks — not once — is what you paid to get in the door. It hands the exact same “safe” 4% to someone who bought stocks in the wreckage of a crash and someone who bought them at a giddy all-time high. Those two people are not running the same experiment. The rule just pretends they are.

This is the valuation trap, and it’s the reason a rule that’s genuinely useful most of the time gets quietly dangerous at exactly the moments people most want reassurance. Let me walk you through it, because the trap is real and the internet’s panic about it is mostly nonsense, and you deserve both halves of that.

First, credit where it’s due

The 4% rule earned its fame. It comes out of the research we dug into in the constant-dollar post and the fuller history: run a stock-and-bond portfolio through every 30-year window in the historical record, and a 4% inflation-adjusted draw survived the overwhelming majority of them — including some genuinely brutal starting decades. As a back-of-the-envelope tool for turning “what do I spend?” into “how big a pot do I need?”, it’s brilliant. I use the 25× shorthand all the time. I’m not here to tell you it’s dead. The “4% rule is dead” crowd is selling fear, and fear is a terrible financial advisor.

What I am here to tell you is that the rule averages away the one thing you don’t get to average: you only live through one retirement.

The blind spot: you only get one slice

The 4% number is a survivor of the whole historical distribution. But you don’t retire into the whole distribution. You retire into a single thirty-year slice of it, and which slice you draw is not random — it’s heavily tilted by how expensive stocks are on the day you start.

That’s the part the rule refuses to look at, and it matters because of a stubborn empirical pattern: the price you pay for the market is one of the better predictors of the returns you get out of it. Buy when stocks are cheap relative to their earnings and history has been kind. Buy when they’re expensive and history has, on average, handed back thinner returns for a good long while. When researchers sort retirements by how pricey the market was on day one — the CAPE-based lens we covered at the end of the last series — the “safe” rate stops being a constant. It slides. And the most expensive starting points in the record produced some of the lowest safe rates the data has ever coughed up.

So “4% survived history” and “4% is safe for your retirement” are two different claims, and the gap between them is exactly the width of the valuation you’re buying at.

Where we are, without the theatrics

I’m not going to throw a scary precise number at you, because precise numbers about a market this far from its own history are false confidence dressed up as rigour. Here’s the honest version: by most sober measures, stocks today are expensive relative to their own long-run average — we’re up in the thin air the market only visits occasionally, the kind of altitude that has historically preceded stretches of underwhelming returns. Not “a crash is coming.” Nobody knows that. Just: the odds that the next decade is a below-average one are tilted higher than usual, and the 4% rule is blind to that tilt.

Could it be different this time? Sure. Maybe earnings keep sprinting and grow into the valuation. Maybe. But “maybe it’s fine this time” is the single most expensive sentence in the history of investing, and you don’t hand it the keys to a plan that has to last thirty or fifty years.

Why expensive markets actually bite

Here’s the mechanism, because “valuations are high” is too abstract to act on. A retirement isn’t broken by a bad average return — it’s broken by a bad early one. That’s sequence-of-returns risk, and it’s the whole ballgame.

When you’re drawing a fixed inflation-adjusted paycheque and the market sags in your first few retired years, you’re forced to sell more and more shares at depressed prices just to cover the bills. Those shares are spent and gone; when the recovery finally comes, they aren’t there to ride it. A rough patch early can permanently hollow out a portfolio in a way the identical rough patch late never could.

Now connect it: a below-average decade is most likely precisely when you buy in expensive. High valuations and weak early returns tend to show up together. So today’s frothy market isn’t a guarantee of disaster — it’s a raised probability that a new retiree hits the exact bad-sequence conditions the 4% rule is least equipped to survive.

So what do you actually do about it?

Not panic. Not gold bars in the garden. Not a spreadsheet that assumes the last fifteen years repeat forever.

You go after the actual problem, which — read that mechanism again — is being forced to sell shares into a weak market to eat. Every real defence against sequence risk is some flavour of “don’t be a forced seller at the bottom”: a cash buffer, a bond tent, the willingness to trim spending in a bad year. But there’s a more structural move, one that lets you barely have to sell shares at all: build a retirement that pays you in cash the businesses generate — money that shows up whether the market is euphoric or terrified, whether you bought cheap or dear — instead of cash you have to raise by liquidating shares at whatever price a jumpy market is offering that morning.

That’s the case for dividend growth investing, and it’s where this little series is headed. It doesn’t repeal the valuation trap by magic — nothing does, and I’ll be honest about its limits as we go. But it changes the question you wake up to from “please, market, don’t sag while I’m selling” to “my businesses just mailed me a raise; the ticker can do whatever it likes today.” At a market this expensive, that’s a much better question to be asking.

We start building it in the next post. Or, if you’d rather see how a plain 4% draw behaves against your portfolio across thousands of market paths — including the ugly expensive-start ones — you can build your portfolio and stress-test it yourself.