Rebalancing Strategies: How to Stay on Track and Boost Returns
A 60/40 portfolio that was never rebalanced from 2000 to 2020 would have drifted to 78/22, drastically changing its risk profile. Rebalancing annually captures a 0.5% to 1.5% rebalancing bonus over the long term. Here is how to do it right.
Rebalancing is the process of realigning your portfolio back to its target asset allocation after market movements have caused it to drift. If your target is 60% stocks and 40% bonds, and stocks rally to make the allocation 70/30, rebalancing means selling some stocks and buying bonds to return to 60/40. This discipline forces you to sell assets that have become expensive and buy assets that have become cheap — systematically capturing a rebalancing bonus over time.
There are three main rebalancing strategies. Calendar rebalancing is the simplest: rebalance on a fixed schedule — quarterly, semi-annually, or annually. Research by Vanguard shows that annual rebalancing provides most of the benefit with minimal costs and taxable events. Threshold rebalancing triggers a rebalance when any asset class deviates by a set percentage from its target (commonly 5% absolute or 20% relative). Hybrid rebalancing combines both: check thresholds quarterly, rebalance annually regardless. The optimal approach depends on your tax situation, account type, and personal tolerance for drift.
Real-world example: An 80/20 stock/bond portfolio in 2020 using VTI and BND. In March 2020, stocks crashed 34%, shifting the allocation to roughly 68/32. A threshold-based rebalancer would have sold bonds and bought stocks at the bottom, capturing a significant rebalancing bonus. By December 2020, stocks had recovered, and the portfolio that rebalanced would have outperformed the buy-and-hold portfolio by approximately 4% that year. In tax-advantaged accounts like IRAs, this rebalancing triggers no tax consequences. In taxable accounts, use new contributions and dividend reinvestment to rebalance rather than selling.
Tax-Efficient Rebalancing Strategies
Rebalancing in taxable accounts requires careful planning to avoid unnecessary capital gains taxes. The most tax-efficient strategies include: directing new contributions to underweight asset classes (e.g., if stocks are overweight, buy only bonds with new money); using dividend reinvestment to rebalance (reinvest US stock dividends into international or bond funds); tax-loss harvesting simultaneously (sell losing positions to realize losses while rebalancing); and rebalancing within retirement accounts first (401k, IRA) where trades are tax-free. For most investors, a once-per-year rebalance using new contributions and dividend redirection avoids tax issues entirely. If you must sell in a taxable account, prioritize selling lots with the smallest gains or use specific identification to minimize tax impact. The rebalancing bonus must be weighed against tax costs — a 5% drift before rebalancing in taxable accounts is a reasonable threshold to avoid excessive trading.
FAQs
How often should I rebalance my portfolio?
Most research recommends annual rebalancing. Vanguard's 2015 study found that annual rebalancing captures 80-90% of the potential rebalancing benefit while minimizing trading costs and taxable events. Quarterly rebalancing adds marginal benefit with higher costs. Threshold-based rebalancing (triggering at 5% drift) works well for more active investors. If you use target-date funds or robo-advisors, rebalancing happens automatically — these are excellent options for hands-off investors.
What is the rebalancing bonus?
The rebalancing bonus is the incremental return generated by systematically selling overperforming assets and buying underperforming ones. Studies show this adds 0.5% to 1.5% annually over a buy-and-hold approach, depending on the volatility of the assets and the rebalancing frequency. The bonus is largest during periods of high volatility with strong mean reversion (like 2008-2009 or 2020). The bonus comes from volatility harvesting — capturing the difference between arithmetic and geometric returns by maintaining constant weights.
Should I rebalance if it triggers capital gains taxes?
Ideally, avoid taxable rebalancing by using new contributions, dividend reinvestment, and rebalancing within tax-advantaged accounts first. If you must sell in a taxable account, weigh the cost of capital gains against the portfolio drift. A good rule: allow a wider 5-10% drift threshold before rebalancing in taxable accounts. Use specific identification of tax lots to sell shares with the smallest gains. Consider donating appreciated shares to charity instead of selling them. For most investors, annual rebalancing with new money avoids taxable events entirely.