What are the main portfolio rebalancing strategies and how do you choose between them?

Rebalancing is the process of realigning portfolio weights back toward the strategic asset allocation (SAA) after market movements cause drift. The choice of rebalancing strategy involves a tradeoff between discipline, transaction costs, and risk control.

Three Main Approaches:

1. Calendar Rebalancing

Rebalance at fixed intervals (monthly, quarterly, annually) regardless of how far weights have drifted.

• Pros: Simple, predictable, easy to implement
• Cons: May rebalance when drift is trivial (wasting on costs) or wait too long when drift is extreme
• Best for: Smaller portfolios, investors with limited governance resources

2. Percentage-of-Portfolio (Threshold) Rebalancing

Rebalance only when an asset class weight deviates beyond a predefined corridor around the target.

• Example: Target equity = 60%, corridor = ±5%. Rebalance only when equity weight falls below 55% or rises above 65%.
• Pros: Only trades when meaningful drift occurs, more cost-efficient
• Cons: Requires continuous monitoring; corridor width is a judgment call
• Best for: Institutional investors with robust monitoring systems

3. Tactical Rebalancing (TAA Overlay)

Adjust weights based on short-term return expectations, intentionally allowing or creating deviations from SAA.

• Example: Overweight equities by 5% during early economic recovery, underweight during late cycle
• Pros: Potentially enhances returns if the manager has forecasting skill
• Cons: Requires genuine skill (most managers fail to add value), introduces tracking error vs. SAA
• Best for: Sophisticated institutions with dedicated macro research teams

Setting Corridor Widths — Key Factors:

Example — Breckenridge Pension Fund:

SAA: 55% equity, 35% bonds, 10% real estate. Corridors: ±5% for equity, ±3% for bonds, ±2% for real estate.

After a bull market quarter:

• Equity drifts to 62% (breaches 60% upper band)
• Bonds drift to 30% (breaches 32% lower band)
• Real estate stays at 8% (within corridor)

Action: Sell equities, buy bonds. No action on real estate.

Cost-benefit analysis: Studies show that percentage-of-portfolio rebalancing generally dominates calendar rebalancing because it trades only when necessary. Optimal corridors are typically 3-5% for liquid assets and wider for illiquid ones.

Practice rebalancing calculations in our CFA Level III question bank on AcadiFi.