What Rebalancing Means in Plain English
When you set up an investment portfolio, you decide how to divide it — maybe 80% stocks and 20% bonds. That’s your target allocation, calibrated for your timeline, goals, and risk tolerance. But markets don’t hold still. Stocks have a strong year and grow to 88% of your portfolio. Bonds shrink to 12%. You’re no longer invested the way you intended.
Rebalancing means bringing it back. You sell some of the overperforming asset (in this case, stocks) and buy more of the underperforming one (bonds) until you’re back at 80/20. Your portfolio is realigned with your original plan.
This feels counterintuitive — you’re selling what’s been winning and buying what’s been lagging. But you’re not making a prediction about which will do better next. You’re maintaining the risk level you decided on, rather than letting drift push you somewhere riskier than you want to be.
How Rebalancing Works
There are two common approaches. Time-based rebalancing means you check and rebalance on a fixed schedule — once a year is the most common. Threshold-based rebalancing means you rebalance when any asset class drifts more than a set amount (5% is a typical threshold) from its target.
Either works. Research shows that rebalancing frequency doesn’t dramatically change outcomes as long as you do it consistently. Annual rebalancing is simple and sufficient for most people.
The mechanics: in a tax-advantaged account (IRA or 401k), you can buy and sell freely without triggering taxes. This is the ideal place to rebalance. In a taxable brokerage account, selling appreciated assets creates a taxable capital gains event. You can minimize this by directing new contributions toward underweighted asset classes instead of selling, letting new money rebalance the portfolio without triggering taxes.
Why Rebalancing Matters to You
Without rebalancing, your portfolio becomes increasingly stock-heavy as stocks outperform bonds over long periods. For a 30-year-old targeting 80/20, that’s intentional. For a 60-year-old approaching retirement who still intends to be 60% stocks, an unchecked portfolio that’s drifted to 80% stocks represents more risk than they planned for — and more vulnerability if a crash happens right before retirement.
Rebalancing enforces the discipline of your original plan. It also has a secondary effect: it mechanically forces you to buy low and sell high — buying the asset class that’s underperformed and selling what’s overperformed. This isn’t a timing strategy; it’s a consequence of maintaining a fixed allocation.
Target-date funds handle rebalancing automatically, which is one of their main advantages for hands-off investors. If you’re using a target-date fund as your entire portfolio, you don’t need to worry about rebalancing.
Quick Example
On January 1, your portfolio is worth $100,000: $80,000 in a stock index fund and $20,000 in a bond fund (80/20).
After a strong stock market year, your portfolio grows to $115,000: $97,750 in stocks and $17,250 in bonds (now 85/15 — not what you planned).
To rebalance back to 80/20, you’d sell about $5,750 of stocks and buy $5,750 of bonds, returning to $92,000 in stocks and $23,000 in bonds. You’re back to 80/20.
Next year if stocks struggle and bonds hold steady, the same logic applies in reverse — you’d buy stocks with bond proceeds. You’re always buying what’s cheaper relative to your target.
Common Misconceptions
- “Rebalancing requires frequent trading.” Annual rebalancing is plenty for most investors. Over-rebalancing monthly or quarterly adds transaction costs and complexity without meaningfully improving outcomes. Set a calendar reminder once a year and review then.
- “Selling winners is a bad idea.” Rebalancing isn’t a call on which asset will do better. It’s enforcing your original risk decision. Letting stocks grow unchecked doesn’t mean you’re a better investor — it means you’re taking on more risk than you planned. When that risk eventually materializes (and markets do correct), you’ll wish you had rebalanced when you had the chance.