Spending guardrails explained

Guardrails are pre-agreed rules for when to change your spending. You decide in advance: if my investments fall below this balance, I'll cut. If they rise above that balance, I'll give myself a raise. Between the two, I leave spending alone.

The point isn't to react to every market move. It's the opposite. Guardrails let you ignore most of the noise, because you already know which move would matter.

Why fixed spending is fragile

The simplest plan spends the same inflation-adjusted amount every year, whatever happens. It's easy to follow. It's also rigid in both directions.

If markets fall early in retirement, fixed spending keeps withdrawing the same dollars from a shrinking portfolio. That's how most plans fail. If markets do well, fixed spending never lets you enjoy it, and many retirees end life with far more than they meant to leave.

Guardrails fix both problems with small, rule-based changes.

Two kinds of guardrails

Withdrawal-rate guardrails. An early version, published in 2006 research, compares your current withdrawal rate to your starting rate. If the rate rises 20% above where you started, you cut spending by 10%. If it falls 20% below, you raise spending by 10%. It's simple and well studied. The app offers it as a strategy to compare.

Risk-based guardrails. A newer approach asks a better question: what's the chance my current spending will need a cut later? The guardrails are the balances where that chance becomes too high or comfortably low. Because the question includes your age, your remaining guaranteed income and your planned expenses, the guardrails adapt as your situation changes.

The Spending guardrails screen uses risk-based guardrails.

How the app sets your guardrails

It starts with your comfort level, the chance of a future cut you're willing to accept:

Then it works out three things from your plan:

1. Your spending level. The monthly spending where the chance of a later cut equals your comfort level.
2. The lower guardrail. The investment balance at which the chance of a cut, at that spending, would reach 75%. Below it, a cut is likely enough that it's better to make a small one now.
3. The upper guardrail. The balance at which the chance of a cut falls to zero. Above it, your spending is safer than you need it to be, so a raise is reasonable.

When a guardrail is crossed, spending goes back to the level that matches your comfort level at the new balance. The change is at least 5% of spending, so you don't make tiny adjustments, and it never overshoots the comfortable level.

A worked example

Priya and Sam are 67 and both retired. Their investments are $1,500,000. Social Security covers part of their spending, and the rest comes from savings. At the Balanced comfort level, the app suggests $7,200 a month in total spending.

Their guardrails come out like this. The figures are invented for illustration:

Notice the cut is small: about 8%. A 24% fall in their investments leads to an 8% cut in spending, not a 24% cut, because Social Security and their remaining years cushion it.

Now suppose markets fall 26% over the next 18 months. Their balance crosses $1,140,000. They cut spending to $6,600 a month, and the app sets new guardrails around the new level. If markets recover, they'll reach a new upper guardrail and get a raise.

The set-aside and the ceiling

Two limits shape the numbers:

• Set-aside. By default the app leaves 10% of your investments out of what safe-to-spend and the guardrails count on. Without it, a plan that's precisely "safe" would spend down to almost nothing in its final year. You can change the set-aside, including setting it to zero.
• Ceiling. An optional maximum monthly spend. Raises never go above it. It's useful if you know you won't spend more than a certain amount, however well markets do.

Healthcare, planned one-time purchases and debt payments are paid first. The guardrails apply to the rest of your spending.

What guardrails don't do

• They don't tell you what to cut. That's your call. Most households cut flexible spending such as travel, gifts or dining before essentials.
• They don't remove risk. A very deep or long downturn can cross the lower guardrail more than once.
• They don't replace judgment. A guardrail crossing is a prompt to review, not an order.

The calculation behind them also takes shortcuts. It folds taxes in using last year's ratio of taxes to spending and values guaranteed income at a fixed real rate. The guardrails methodology page explains these choices and how closely they match a full simulation.

How to use guardrails in practice

1. Update balances regularly. Monthly or quarterly is enough. The app compares each update with your guardrails.
2. Turn on alerts. You can get a notice when you're within a chosen distance of a guardrail, so a crossing is never a surprise.
3. Record the change. When you cut or raise, record it in the app. Your guardrails then reset around the new spending.
4. Revisit after big life changes. A death, a move, an inheritance or a new health cost changes the plan. Update it, and the guardrails follow.

Frequently asked questions

How often will a guardrail be crossed?

It depends on markets and your comfort level. The screen shows the chance of a cut and of a raise over the next several years, measured across simulated futures.

Isn't a 75% chance of a cut too late to act?

The lower guardrail is where acting is clearly better than waiting. Because the cut at that point is usually small, waiting until then avoids cutting for market dips that recover on their own.

Can I use guardrails while I'm still working?

Yes. For working households, the guardrails come from simulating the whole plan, including your future savings. They show the balances that would change how much you can spend today without falling off track.