🎯 In 30 seconds: Asset allocation is how you split your money between stocks, bonds and cash. That split decides most of how bumpy your ride will be. People usually set it by two things: when they need the money, and how big a drop they can sit through without selling. Then they rebalance back to it on a schedule.
The three building blocks
Stocks have grown the most over long periods and also fall the hardest. Drops of 30% to 50% have happened several times (see the stock market basics).
Bonds pay interest and usually move less than stocks. They are the shock absorber. They can still lose value when interest rates rise, as they did in 2022.
Cash (savings, money market funds, T-bills) barely moves in price. It is for money with a date on it and for emergencies. Its job is stability and access, not growth.
No single mix is right. The mix is a trade: more stocks means more expected growth and deeper drops along the way.
Match the mix to the date you need the money
The single most useful question is “when will I spend this?” A common way to think about it:
| When you need it | What people commonly hold | Why |
|---|---|---|
| Under 3 years | Cash, CDs, T-bills | No time to wait out a stock crash |
| 3 to 10 years | A blend, often more bonds than stocks near the short end | Some growth, limited damage if markets fall right before you need it |
| 10+ years (retirement) | Mostly stocks, some bonds | Time to recover from drops; growth matters most |
| In retirement | A mix, with a few years of spending in bonds and cash | So you are not forced to sell stocks in a downturn |
One goal, one mix. Your house down payment in two years and your retirement in thirty years can sit in different buckets with different allocations.
Rebalancing: two ways to do it
Markets move your mix without asking. After a good year for stocks, a 60/40 portfolio might be 65/35, which is riskier than you chose. Rebalancing means moving it back.
- Calendar rebalancing: check once a year (a birthday or tax season works) and reset. Simple and easy to remember.
- Threshold rebalancing: reset only when a part drifts more than a set amount, such as 5 percentage points from its target. Fewer trades in calm years, faster action in wild ones.
- With new money: send new contributions to whatever is underweight. This often fixes drift without selling anything.
Worked example
Maria has $100,000 set at 60% stocks and 40% bonds: $60,000 and $40,000. Over a year stocks gain 20% and bonds gain 2%.
| Stocks after a year | $60,000 × 1.20 = $72,000 |
| Bonds after a year | $40,000 × 1.02 = $40,800 |
| Total | $112,800 |
| Stock share now | 63.8% (target 60%) |
| Target stock amount | 60% × $112,800 = $67,680 |
| Move to bonds | $72,000 − $67,680 = $4,320 |
Inside a 401(k) or IRA she can make that switch with no tax. In a regular brokerage account, selling $4,320 of stock that has grown creates a taxable gain, so many people instead point the next few months of contributions at bonds until the mix is back.
Common mistakes
- Picking an aggressive mix in a calm market, then selling in the first crash. Choose the mix you could hold through a 30% drop.
- Counting each account separately. Look at all accounts together as one portfolio.
- Rebalancing every week. More trades, more costs, little benefit.
- Forgetting cash goals. An emergency fund is not part of your stock and bond mix.
Want to see how a mix would have behaved in the past? Try the backtest tool.