Calendar rebalancing vs. percent-range rebalancing — pros, cons, and when to use each?

Question

AcadiFi · Accepted Answer

Rebalancing is a crucial implementation topic in Level III. Here's the comparison:

**Calendar Rebalancing**
- **How it works:** Rebalance to target weights on a fixed schedule — monthly, quarterly, or annually.
- **Advantages:**
  - Simple to implement, easy to communicate to governance committees
  - Lower monitoring costs
  - Predictable transaction timing (can batch with other trades)
- **Disadvantages:**
  - May rebalance when unnecessary (if weights haven't drifted much)
  - May miss significant drift between dates (e.g., a market crash mid-quarter)
  - No responsiveness to market conditions

**Percent-Range (Corridor) Rebalancing**
- **How it works:** Set trigger points (corridors) around each target weight. Rebalance only when an asset class drifts beyond its corridor. E.g., if target is 60% equities with a ±5% corridor, rebalance when equities drift above 65% or below 55%.
- **Advantages:**
  - Only trades when needed — more cost-efficient
  - Captures significant drift promptly
  - Theoretically superior risk control
- **Disadvantages:**
  - Requires continuous monitoring
  - Corridor width decisions are subjective
  - Can trigger frequent trades in volatile markets (higher costs)

**Setting Corridor Width — Key Factors:**

Wider corridors are appropriate when:
- Transaction costs are high
- Asset class has high correlation with the rest of the portfolio
- Taxes on rebalancing are significant
- The investor has high risk tolerance

Narrower corridors when:
- Transaction costs are low
- Asset class has high volatility (bigger drift risk)
- The asset is weakly correlated with the portfolio (drift means more risk change)
- The investor has low risk tolerance

**Example:** A pension fund with a 40% allocation to emerging market equities (high volatility, high transaction costs). You'd set a relatively *wider* corridor (say ±7%) because the cost of frequent rebalancing outweighs the benefit. But for a 30% allocation to US treasuries (low cost, low volatility), a *narrower* corridor (±3%) is appropriate.

**Exam Format:** Expect vignettes asking you to recommend corridor widths for different asset classes within the same portfolio, or to compare a calendar approach vs. corridor approach for a specific investor.

Practice rebalancing scenarios in our CFA Level III question bank.

Calendar rebalancing vs. percent-range rebalancing — pros, cons, and when to use each?

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