When people obsess over which fund to buy, they’re usually focused on the wrong decision. The choice that actually shapes your results is your asset allocation — how you split your money between stocks and bonds. It controls both how much your portfolio grows and how hard it lurches when markets fall, and the right mix changes as you age. Let me make it concrete.
What asset allocation is
Asset allocation is the division of your portfolio among the main asset types:
- Stocks — higher growth, bigger swings. Your engine.
- Bonds — steadier, lower growth. Your shock absorber.
- Cash — safe, but eroded by inflation over time.
Your mix matters more than your picks. The split between stocks and bonds drives most of your return and most of your risk — far more than which specific fund you choose.
The “minus your age” rule
A simple starting point: subtract your age from about 110 to get your stock percentage. The rest goes to bonds.
| Age | Stocks | Bonds |
|---|---|---|
| 30 | ~80% | ~20% |
| 40 | ~70% | ~30% |
| 50 | ~60% | ~40% |
| 60 | ~50% | ~50% |
| 70 | ~40% | ~60% |
It’s a guideline, not a law — the asset allocation calculator tailors it to your risk tolerance and timeline.
Why the mix shifts with time
The logic is about time to recover, not age itself:
- Young? Decades ahead mean you can ride out crashes — even a brutal year has time to heal. Lean into stocks.
- Near retirement? A crash right before you start withdrawing is dangerous, because you’d be selling while down. More bonds protect the money you’ll need soon.
This is the same sequence-of-returns risk behind the 4% rule: the years around retirement are the fragile ones.
Rebalance to stay on target
Over time, a strong stock run pushes your mix off-target — suddenly you’re taking more risk than you chose. Rebalancing fixes it:
- Check once or twice a year, or when your mix drifts >5% from target.
- Sell a slice of what grew, buy what lagged, back to your target split.
- It quietly enforces “buy low, sell high” and keeps diversification intact.
Beyond the rule
The formula is a floor, not a ceiling. Nudge more aggressive if you have a steady income or a pension and a strong stomach; more conservative if market dips genuinely keep you up at night — because the best allocation is the one you’ll actually hold through a downturn.
The lazy option: target-date funds
If choosing and rebalancing a mix sounds like work, a target-date fund does it for you. You pick the fund with your retirement year in its name, and it holds a diversified mix that automatically grows more conservative as that date nears:
| Build it yourself | Target-date fund | |
|---|---|---|
| Allocation | You choose | Done for you |
| Rebalancing | You do it | Automatic |
| Shift with age | Manual | Automatic |
| Cost | Lowest | Slightly higher |
For many investors — especially beginners — one target-date fund is a complete, hands-off portfolio.
Set your mix
Pick a deliberate allocation and let it guide every contribution. Run yours through the asset allocation calculator, keep your funds low-cost, and read the investing guide to fit allocation into your full plan.
