Ask what makes an asset risky and you will be told about volatility. That answer has a hole in it. Risk is not something an asset has. It is something an asset does, or fails to do, in relation to what you are trying to pay for. Once the objective is a standard of living, cash becomes risky and a long bond becomes safe.
Risky Compared to What?
"Equities are risky." "Cash is safe." Both sentences are missing a word.
Risky compared to what? Safe against what? Risk is a comparison, and every comparison needs two things. Ordinary finance language names only one of them, then quietly fills the other in for you. What it fills in is the nominal value of your portfolio, measured over the next year or so.
That default is not wrong for a bank managing quarterly capital. It is wrong for you, because you are not trying to protect a balance. You are trying to pay for something.
The Objective Comes First
What retirement actually requires is a stream. So much per year, rising with prices, for as long as you live. That is not a pot of money. It is a series of dated, inflation-linked payments, and it is the thing your portfolio exists to deliver.
Merton made the point in 1969 and again in 1971. The investor's problem is not maximising wealth at some horizon. It is sustaining consumption over a lifetime. Risk enters only through the threat to that consumption.
So the question stops being "how much does this asset move?" and becomes "how well does this asset track what I have to pay?"
The Safe Asset Is the One That Copies the Liability
Once the objective is a real spending stream, the safe asset is whatever reproduces that stream. For a long-horizon retiree, that is a long-dated inflation-indexed government bond, not a Treasury bill.
This is the part that sounds backwards and is not. Modigliani and Sutch made the argument in 1966, Stiglitz in 1970, Rubinstein in 1976, and Campbell and Viceira built the modern synthesis on it in 2002. The safe asset depends on the horizon and the objective, and for a spending stream thirty years long, the matching asset is thirty years long too.
The definition matters more than it looks. Whatever you name as the safe asset determines what everything else is. Change the objective and the whole ranking rearranges.
Cash Is Risk-Free in the Wrong Units
Merton draws a distinction worth borrowing. The technical risk-free asset is the one whose return over the shortest trading interval is known with certainty. That is cash, and on that measure it is genuinely risk-free.
The numéraire risk-free asset is the one that delivers the objective you actually have. If the objective is a stable real income for as long as you live, the numéraire risk-free asset is a long inflation-linked bond. Cash is nowhere near it.
Both are risk-free. They differ in what they are risk-free against, and only one of them is measured in the units your life is priced in. That is the whole argument, and it is why calling cash safe is not wrong so much as unfinished.
Cash cannot fund thirty years of real spending. It carries no inflation protection over any horizon that matters, and it has to be reinvested constantly at whatever rate exists on the day.
Both of those are risks against the objective. Your bank balance is stable in the one dimension nobody is asking about, and exposed in the two that decide whether you eat.
The intuition that cash is safe comes from a different question. Cash is excellent at holding its nominal value over a short period, which is what you want from an emergency fund or next year's spending. It is not what you want from money that has to buy groceries in 2050.
And Volatility Is Not Risk
The price of a long inflation-linked bond moves. When real yields rise, it falls, and it can fall a long way.
But the price of your retirement moves the same way at the same time. Higher real yields make future spending cheaper to fund. The asset and the obligation fall together, so the gap between them barely moves, and the gap is the only thing you actually care about.
An asset can be volatile and safe. An asset can be stable and dangerous. Which one it is depends entirely on whether it moves with the thing you are trying to fund.
This is why the standard advice to move into cash and short bonds as you approach retirement can raise your risk rather than lower it. The portfolio gets quieter. The funding gap gets more exposed.
The Awkward Middle
Some holdings do neither job. Nominal bonds do not track inflation-linked spending, and they carry no equity premium. Cash is the same, gold is close to it.
There is a temptation to file these as "in between", as though they sit halfway between safe and risky. They do not. Nothing here hedges the objective, so all of it is risk. What is missing is the compensation.
Call it what it is. Unrewarded risk is risk that pays you nothing for taking it. That is a strictly worse position than owning equities, which at least come with a premium attached, and it is invisible to anyone measuring safety by how quietly a holding behaves.
What This Changes About Measurement
If risk is relative to the objective, then a risk measure has to price the objective first. That is what the funded ratio does. It prices what your spending costs at today's real yields, sets your assets against it, and reports the ratio.
The gap is the risk. Not the standard deviation of your portfolio, not its worst year, but the distance between what you own and what your life costs. Its natural unit is years of your own spending.
That number can improve while your portfolio falls, and it can deteriorate while your portfolio rises. Both happen when the liability moves more than the assets do.
What It Does Not Tell You
This frame names no product and recommends nothing. It says which comparison is the honest one, and leaves what to hold entirely with you.
It also does not promise anything. Pricing your spending against today's real curve tells you where you stand today, at today's yields, on today's assumptions about how long you live. Tomorrow it will say something slightly different, which is the point of measuring it again.
What it does do is stop you from being told a portfolio is safe when nobody has said what it is safe against.
Risk is relative to the objective. If the objective is a standard of living, anything that does not hedge that objective is risky, whatever its price chart looks like. That single move puts cash on the risky side of the line, puts long inflation-linked bonds on the safe side, and turns "how much does this move?" into "how well does this pay for my life?"
Risky compared to what? Compared to the life you want to fund.
This is Post 13 of The Funded Ratio — a series on amifunded.com applying actuarial principles to individual retirement portfolios. Built on Merton (1969; 1971; 1973) on lifetime consumption and hedging demands, Merton (2017) on the technical and numéraire risk-free assets, Breeden (1979) on consumption risk, Modigliani and Sutch (1966), Stiglitz (1970) and Rubinstein (1976) on long bonds as the long-horizon safe asset, and Campbell and Viceira (2002) on intertemporal asset allocation. No financial advice is given. All methods use publicly available academic research and market data.