Bringing your portfolio back to target, without thinking
You picked 80% stocks, 20% bonds. Stocks rally, and suddenly you're sitting at 90/10 without lifting a finger. Rebalancing closes that gap by trimming some stocks and topping up bonds. It is mechanical, it takes ten minutes a year, and it stops you from carrying more risk than you ever agreed to.
The 80/20 that quietly turns into a 95/5
Ten years of a bull market quietly turn an 80/20 into a 95/5. The balance sheet looks great, but the portfolio is now running far more risk than you ever signed up for. When the next drawdown arrives, the hit will be roughly twice as deep. Rebalancing prevents that silent drift: it trims what has surged, refills what has lagged, and stops there.
The two main strategies
Two methods dominate. Pick the one you can actually stick to: the best strategy is the one you will keep applying.
📅 Calendar: on a fixed date
Once a year, say on January 1, you bring the portfolio back to target. Advantage: no decision to make, a calendar reminder is enough. Limit: if nothing has drifted, you pay fees for nothing; if a big move hits in July, you wait six months before reacting.
📊 Threshold: on event
You set a tolerance band, say ±5 points. As long as the 80/20 stays between 75/25 and 85/15, you do nothing. As soon as one class steps outside the band, you rebalance. Advantage: you act when it matters, not before. Limit: you need to check allocation monthly or set up a broker alert.
March 2020: what the rule would have done for you
Between February 19 and March 23, 2020, the S&P 500 dropped 34%. The 80/20 had just slipped to 70/30. If you applied the rule, you sold a portion of your bonds to buy stocks at the bottom. Twelve months later, the index had recovered about 75%. Bonds cost you a little return before the crash. They paid for the shares you bought while everyone else was panicking.
⚠️ "Doing nothing" is not a passive strategy
Letting it ride means letting the market choose your allocation for you. After five years of tech-stock gains, your "balanced" portfolio has become a concentrated bet on a single sector. When that sector corrects, you discover the risk you were carrying without knowing it.
Key Takeaways
- 1Rebalancing keeps your allocation on target. It is a risk-control tool, not a performance trick.
- 2Without it, an 80/20 drifts to 95/5 over ten bull years. You end up running risk you never chose.
- 3Once a year, or whenever a class breaches ±5%. Too frequent: wasted fees. Never: hidden drift.
- 4While you are still saving, rebalance by directing fresh contributions to the underweight class. Zero tax, zero fees.
Keep going
Frequently asked questions
Without rebalancing, your allocation drifts with performance: an 80/20 can become 95/5 over a 10-year bull market, exposing you to far more risk than your initial tolerance. Rebalancing maintains your target risk profile and mechanically forces 'sell high, buy low'.
Annual or threshold-based (drift = how far the allocation has moved from target, ±5%) are the standards. Quarterly: too many fees with no proven performance gain. Threshold rebalancing is statistically marginally superior to calendar-based per Vanguard backtesting, but the gap is small. Pick the method you can stick to.
Yes in a regular taxable account: each sale triggers a taxable capital gain. Favor rebalancing via new flows (contribute to the underweight class rather than selling the overweight one). In a tax-advantaged account (IRA, 401k, PEA), no friction: rebalance freely.
Rebalance. That's precisely when rebalancing proves its worth: you sell bonds (relatively high) to buy stocks (low). In March 2020, an 80/20 turned 70/30 after the crash let you buy stocks at the bottom; +75% in 12 months. Discipline beats emotion.