Portfolio Rebalancing
First Seen: February 2011 · Concept: Modern Portfolio Theory · Status: Essential portfolio maintenance
Overview
Portfolio rebalancing is periodically adjusting portfolio back to target asset allocation as market movements cause drift.
Example: Target 80/20 stocks/bonds. After bull market, portfolio is 87/13. Rebalancing sells stocks, buys bonds to restore 80/20.
Why Rebalance?
Risk management: Prevents overexposure to one asset (2000 tech bubble, 2008 housing)
Forced discipline: “Sell high, buy low” (sell winners, buy losers)
Return enhancement: Studies show rebalancing improves risk-adjusted returns
Rebalancing Methods
Calendar rebalancing: Annual (most common), quarterly, monthly
Threshold rebalancing: When allocation drifts 5%+ from target
Hybrid: Check annually, rebalance if threshold exceeded
Tax Considerations
Tax-advantaged accounts (401(k), IRA): Rebalance freely (no capital gains taxes)
Taxable accounts: Be strategic:
- Use new contributions to buy underweight assets
- Tax-loss harvest losers
- Consider waiting until long-term capital gains (1 year)
Evidence & Debate
Vanguard research (2015): Annual rebalancing slightly outperformed never rebalancing (but not significantly). Main benefit is risk control, not returns.
FIRE community split:
- Pro-rebalancing: Maintains risk profile, prevents FOMO chasing
- Anti-rebalancing: Selling winners early, transaction costs, tax inefficiency
Compromise: Rebalance with new contributions (don’t sell, just direct new money to underweight assets)
2022 Example
Portfolio drift 2021: 90% stocks, 10% bonds (bull market)
2022 bear market: Stocks down 20%, bonds down 13%
Rebalancers: Bought stocks at bottom (sold bonds 2021, bought stocks 2022)
Non-rebalancers: Remained overweight stocks through decline
Sources
- Vanguard: “Best practices for portfolio rebalancing” (2015)
- Bogleheads rebalancing wiki
- r/Bogleheads rebalancing threads