Rebalancing Discipline¶

Why It Matters¶

Without rebalancing, portfolios drift toward whatever has performed well, concentrating risk. Tech stocks quintupled? Your intended 20% allocation is now 50%, and you have massive concentration risk. Rebalancing corrects the tendency to ride winners too long and avoid losers. It's a mechanism for buying low and selling high without predicting anything.

The Key Move¶

Set target allocations for each portfolio component based on strategy (not recent performance). Monitor actual allocations. When any component drifts beyond a threshold (e.g., ± 5 percentage points from target), rebalance: sell the excess from outperformers, buy the deficit in underperformers. Execute systematically on a schedule (quarterly, annually) or when threshold breaches occur. Ignore feelings about whether this seems "right."

Classic Application¶

Stock-bond rebalancing. Target 60% stocks, 40% bonds. Stocks rally, portfolio is now 70-30. Rebalancing sells 10% of stocks, buys bonds—capturing the stock gains and resetting risk exposure. Over decades, this mechanical process adds ~0.5% annual return from the volatility alone (volatility harvesting).

Surprising Application¶

Attention allocation across life domains. Set target allocations: 40% work, 30% relationships, 20% health, 10% learning. Quarterly review reveals work has drifted to 60%, relationships to 15%. Rebalancing requires cutting work commitments and scheduling relationship time, even though work feels more "important" right now because it's been successful. The discipline prevents work from crowding out everything else simply because it's going well.

Failure Modes¶

Transaction costs can exceed benefits if rebalancing too frequently or with small drifts. Doesn't work in trending markets—you sell winners early and buy losers that keep losing. Assumes mean reversion that may not exist (selling Amazon for 20 years would have been costly). Ignores tax consequences (realizing gains to rebalance triggers taxes). Mechanical rules don't account for regime changes—rebalancing into value stocks during a growth regime hurts.

Go Deeper¶

Bernstein & Wilkinson, "Diversification, Rebalancing, and the Geometric Mean Frontier" (1997); Jaconetti et al., "Best Practices for Portfolio Rebalancing" (Vanguard, 2010)