Age and investing
"Own your age in bonds." It's the oldest rule of thumb in personal finance — and like most rules of thumb, it's half a good idea wearing a lab coat. Here's the part that holds up, and the part that doesn't.
The rule, and where it came from
The classic version: hold a percentage of bonds equal to your age. Forty years old, 40% bonds; sixty, 60%. The instinct behind it is sound — take less market risk as you get older — and as lifespans stretched, people nudged it to "110 (or 120) minus your age" in stocks to avoid being too cautious too early. Target-date funds are just this idea, automated: a "glide path" that slowly shifts from stocks toward bonds as a retirement date approaches.
What actually changes with age
It isn't the number on your birthday. It's your time horizon — how long until you need the money. That matters for one concrete reason:
- Time to recover. Markets fall regularly and, historically, have recovered given enough years. A 30-year-old riding out a crash has decades for it to matter less. Someone withdrawing next year does not.
- Sequence-of-returns risk. This is the one that earns the caution. A bad crash early in retirement — while you're selling to live on — does far more lasting damage than the same crash later, because you lock in losses on money you're spending. Same average return, very different outcome, purely because of the order.
Where the rule breaks down
Rules of thumb are crude by design. A few honest caveats:
- Risk capacity isn't risk tolerance. Your age says something about how much risk you can afford to take; it says nothing about how much you can stomach. A portfolio you bail out of in a panic is riskier than the numbers suggest.
- Your paycheck is a bond. When you're young, your future earnings act like a stable, bond-like asset — which is part of why the young can afford more stocks than a pure age rule implies. As you near retirement, that "bond" runs out.
- Retirement isn't an end date. Money you'll spend at 90 still has a 25-year horizon at 65. Going all-bonds the day you retire can leave you exposed to a slower, quieter risk: inflation eating the pile you stopped growing.
The short version
- The kernel of truth: take less risk as your time horizon shortens. That part is real.
- What actually matters isn't age but horizon and sequence-of-returns risk near retirement.
- "Age in bonds" is a starting point, not a prescription — capacity, tolerance and future income all bend it.
- Going fully conservative too early swaps market risk for inflation risk — see inflation.
Sources
- Bogle, J. — The Little Book of Common Sense Investing (on age-based allocation and its limits).
- Vanguard — target-date "glide path" research and the rationale for shifting allocation with time horizon.
- Pfau, W. — research on sequence-of-returns risk in early retirement.