Asset Allocation by Age: Why “100 Minus Your Age” Stopped Working

Why Asset Allocation Beats Stock Picking

Few questions matter more to a portfolio’s long-term fate than asset allocation by age: the split between equities, bonds and cash that should shift as an investor moves through life. Most people spend far more energy agonising over which stock to buy than over that split, even though the split does almost all the work.

That is not an opinion. In a landmark study published in 1986 and updated in 1991, Gary Brinson, Randolph Hood and Gilbert Beebower examined the returns of large pension funds and found that policy mix, the broad allocation between asset classes, explained more than 90% of the variation in returns over time. Security selection and market timing combined accounted for the rest.

More recent evidence points the same way. In its scorecard covering the 15 years to the end of 2024, S&P Dow Jones Indices found that not one of the 22 categories of US equity funds it tracks had a majority of active managers beating their benchmark, and more than 90% of large-cap funds lagged the S&P 500 over that period, a gap examined in detail in Index Funds vs Actively Managed Funds: What 30 Years of Data Actually Prove. Picking the right manager, let alone the right stock, is a much harder game than picking the right mix.

Diversification across asset classes removes company-specific risk for nothing. Investors are only paid, on average, for the risk they cannot diversify away: the risk of the market itself.

How Age Shapes Risk Capacity

Age matters because it determines time horizon, and time horizon determines how much volatility a portfolio can absorb without permanent damage.

A sharp fall in a broad equity index feels identical whether an investor is 25 or 65. The consequences are not. A 25-year-old has decades of future paychecks to invest at the new, lower prices, turning a downturn into a discount. A 65-year-old who needs to draw down the portfolio within a few years has no such luxury; a fall that coincides with the start of retirement can do damage that decades of later gains cannot fully repair.

Economists describe this with the idea of an economic balance sheet. Total wealth equals human capital, the present value of future earnings, plus financial capital, the money already saved and invested. The young are rich in human capital and poor in financial capital. Over a working life, human capital depletes as financial capital builds, and the portfolio’s role shifts from grower to preserver.

From “100 Minus Age” to the Modern Glide Path

The oldest rule of thumb in personal finance is also the simplest: subtract your age from 100, and that is the percentage of a portfolio that belongs in equities, with the rest in bonds. A 30-year-old holds 70% equities; a 70-year-old holds 30%. It required no spreadsheet and no adviser, which is precisely why it spread.

It also predates two things that now matter enormously: low-cost index funds and much longer lifespans. A 65-year-old retiring today may need a portfolio to last 30 years or more, and a 35% equity allocation, sitting mostly in bonds yielding modestly above inflation, risks losing purchasing power over a retirement that long. The 10-year Treasury yield stood at about 4.55% in mid-June 2026, and with consumer prices running hot enough that the real, after-inflation return on that yield is thinner than the headline number suggests, an overly conservative mix carries its own risk.

For 2026, many advisers now start from 110 or 120 minus age rather than 100, shifting the entire glide path several years younger. Target-date funds automate the same idea, but the mechanics vary: “to” funds reach their most conservative mix at the retirement year itself, while “through” funds keep de-risking for another decade or more on the assumption that the money still needs to grow after the saving stops.

The table below shows how the equity share of a portfolio differs under the old rule and its two modern variants.

Asset Allocation by Age, Stage by Stage

Early career, roughly ages 20 to 35, is the growth phase. Human capital is at its peak and financial capital is small, so even a severe drawdown does little lasting damage; an allocation of 90% to 100% equities is common advice for this stage, with any bonds added mainly to build the habit of holding a diversified portfolio rather than to dampen volatility.

Mid-career, roughly 35 to 50, is when mortgages, children and rising lifestyle costs compete with peak earnings. A modest bond allocation, often in the 15% to 30% range, starts to cushion the portfolio without giving up much growth.

Pre-retirement, roughly 50 to 65, is where sequence-of-returns risk becomes the dominant concern. A severe market fall in the years immediately before retirement leaves little time to recover before withdrawals begin, which is why allocations typically shift toward 50% to 70% equities. After 65, the priority becomes generating income while keeping enough growth, usually at least 30% to 40% equities, to outpace inflation over a retirement that can easily run past 25 years.

The table below summarises typical allocation ranges and the goal each life stage is built around.

Bonds, Equities and the Inflation Problem

Bonds are often described as the safe part of a portfolio, but safety depends on which risk is being measured. A high-quality government bond carries little credit risk. It carries plenty of interest rate risk: when yields rise, the price of existing bonds with lower coupons falls, and the longer the bond’s duration, the larger the fall.

That risk has been on display recently. Yields on long-term Treasuries have moved sharply over the past two years, a shift charted in Bond Yields Are at a 15-Year High. Here Is How Fixed Income Investing Works, and bondholders who assumed their allocation was immune to volatility learned otherwise.

Equities respond to inflation differently. Companies with real pricing power can raise prices roughly in line with costs, so their revenues and, eventually, dividends keep pace with inflation in a way a fixed coupon cannot. That is the main reason equities remain the only major asset class with a multi-century record of positive real returns, and why even retirees are usually advised to keep a meaningful equity allocation rather than retreat entirely into cash and bonds.

Building Your Own Age-Appropriate Portfolio

Two psychological traps tend to push investors away from their ideal allocation. Young investors who have only seen rising markets often mistake a bull market for skill, concentrating in a handful of speculative positions rather than building a diversified base, then panic-sell in the first real downturn they experience. Older investors feel the asymmetry of loss aversion, the well-documented tendency for a loss to hurt roughly twice as much as an equivalent gain feels good, and retreat into cash, where inflation quietly erodes their savings instead.

Risk tolerance and risk capacity are not the same thing. Tolerance is psychological: how much of a paper loss an investor can stomach without changing course. Capacity is mathematical: how much of a loss the plan can absorb without compromising the goals it is meant to fund. Age mostly determines capacity. Personality determines tolerance. A useful portfolio respects both.

A practical framework starts with the time horizon: count the years until the money is needed, and whether it will be withdrawn as a lump sum or spent down over decades. From there, a baseline allocation, such as 110 or 120 minus age, gives a starting equity percentage. That number then gets adjusted for job stability, pension income and the size of an emergency fund, before settling on a rebalancing rule: either a fixed date each year, or a shift whenever an asset class drifts more than five percentage points from its target.

The 100-minus-age rule was not wrong so much as built for a world with shorter retirements and higher bond yields. Asset allocation by age is less about the number on a birthday cake and more about matching risk capacity to time horizon, and the arithmetic behind that match has simply moved on.