When and How to Rebalance

Rebalancing means bringing a drifted portfolio back to target allocations. After a strong year for stocks, the equity slice grows beyond target — rebalancing sells some equity and buys what's underweight.

Two main approaches

• Calendar: Rebalance every 12 months (or every 6, or quarterly). Simple; predictable.
• Threshold: Rebalance whenever an allocation drifts > 5% absolute (or > 25% relative) from target. Better risk control; requires monitoring.

What the research shows

Vanguard and others have shown that the specific rule matters less than having any rule. The "rebalancing bonus" — additional return from rebalancing — is small but real (0.1–0.5%/year). The behavioral benefit (forcing discipline) is probably larger.

How to minimize cost

1. Rebalance with new contributions first. Direct new money to underweight buckets — no taxes, no transaction friction.
2. Use tax-advantaged accounts for major rebalancing — no capital gains realized.
3. In taxable accounts, sell only to harvest losses or when drift is large. Use dividend cash to rebalance opportunistically.

What to avoid

Constant tinkering. Rebalancing once a year (or less) when triggered by a 5% drift captures nearly all of the benefit. More frequent rebalancing adds friction without adding return.

A worked example: rebalancing after 2020

Suppose your target was 60% US stocks / 40% bonds, with $500,000 invested at the start of 2019. After two strong years, by January 2022 the same portfolio had drifted to roughly 73/27. The "tech bubble" of 2020–2021 had quietly increased your equity risk by a third without you noticing.

Rebalancing to 60/40 in January 2022 — selling stocks, buying bonds — would have spared you about half the damage of the 2022 bear market in which both stocks and bonds declined but stocks declined more. The investors who didn't rebalance discovered they were running an 80/20 portfolio just as it lost 25% of its value.

Rebalancing isn't about return enhancement. It's about staying in the risk seat you actually agreed to be in.

Calendar vs. threshold rebalancing

Two main approaches, both work:

• Calendar rebalancing. Rebalance on a fixed schedule — typically once a year. Simplest. Predictable. Works.
• Threshold rebalancing. Rebalance whenever any allocation drifts more than ~5% absolute (or 25% relative) from target. Better risk control during volatile periods. Requires monitoring.

Vanguard's most-cited study compared monthly, quarterly, annual, and threshold-only rebalancing across many decades and concluded: the specific rule matters far less than having one. Annual rebalancing captures 95% of the benefit of more frequent approaches with one-tenth the friction.

The rebalancing bonus: real but small

Beyond risk control, rebalancing produces a small but real return premium — the "rebalancing bonus." It works because you systematically sell what's gone up (high) and buy what's gone down (low). Over 30 years of mean-reverting markets, the bonus typically adds 0.1–0.5%/year.

It's nothing compared to the cost of not rebalancing and getting caught in a bear market with 20% more equity than you wanted. The risk-control case dwarfs the return-enhancement case.

How to rebalance cheaply

1. First, redirect new contributions. If stocks are over-allocated and bonds under, send all new money to bonds for the next few months. Often this alone restores the target with zero trades and zero tax.
2. Use dividends. Have dividends pay to a cash account instead of auto-reinvesting. Manually direct them where rebalancing needs them.
3. Rebalance inside tax-advantaged accounts first. Trading inside a 401(k) or IRA has no tax consequence. Make all your big moves there.
4. In taxable, harvest losses simultaneously. If you must sell a stock fund to rebalance, look for a losing lot to harvest at the same time.
5. Tax-loss-rebalance combo. Sometimes you can sell a losing asset (harvest the loss) and buy back into the correct allocation, achieving rebalancing + TLH in one move.

Common rebalancing mistakes

• Rebalancing too often. Monthly rebalancing in taxable accounts creates short-term gains, transaction friction, and zero added benefit over annual.
• Letting drift go for 5+ years. The "retired millionaire" with a 95/5 stock/bond portfolio at age 70 is usually someone who haven't rebalanced since their 50s.
• Selling winners in taxable without checking the tax bill. A 5% rebalance with a 30% gain triggered creates a 1.5% tax drag. Often not worth it.
• Rebalancing during panic. If you want to rebalance during a crash because "stocks are now cheap," good — that's the buy-low part working. But don't deviate from your written plan in the moment.
• Conflating rebalancing with timing. Rebalancing brings you back to a plan, it doesn't choose when to enter or exit asset classes.

Frequently asked questions

Do target-date funds rebalance automatically?

Yes. The whole point of a TDF is that it does both rebalancing and de-risking with age, automatically and free. For investors who'd otherwise neglect rebalancing, a TDF often outperforms a self-managed portfolio simply because the rebalancing happens.

Should I rebalance when one allocation is just 2% off?

No. Most studies suggest a 5% absolute threshold is the sweet spot. Smaller deviations aren't worth the transaction costs.

What about taxes — do they kill the rebalancing benefit?

In tax-advantaged accounts, no tax cost. In taxable, you can usually avoid it with new contributions and dividend redirection. If you must realize gains, the tax cost is real but typically smaller than the risk-control benefit of staying near target.

How do I rebalance into a specific bond fund vs. just BND?

Pick a target bond mix once (e.g., 50% intermediate Treasury, 50% total bond) and treat it as the rebalancing target. Don't tinker with the mix during rebalancing — that's market timing dressed up.

Putting this into practice this week

The hardest part isn't understanding the concept — it's making one small change before you forget. Pick the single most relevant action below and put it on your calendar. Future you will thank present you for choosing one thing and doing it, instead of nothing while planning everything.

• Open a high-yield savings account if you don't have one. Twenty minutes.
• Increase your 401(k) contribution by 1 percentage point. Five minutes.
• Sign up for the Krovea Sunday letter and bookmark this article.
• Walk through the relevant Krovea calculator with your actual numbers.

Key takeaways for your action plan

• Start now, not when the market "feels right." The optimal entry point is unknowable in advance.
• Automate the decision so behavior is removed from the equation.
• Match your strategy to your time horizon, not to recent headlines.
• Tax-advantaged accounts come first; taxable strategies are the finishing touches.
• Review your plan annually, ignore it the other 364 days.

The bottom line

Rebalancing is the most important habit in long-term investing that almost nobody talks about. It enforces discipline, controls risk, and (as a side effect) earns a small premium. Pick a rule — annual or threshold — write it down, and follow it for 30 years. That single discipline beats most of what people obsess about online.