What rebalancing triggers should I use for an immunized bond portfolio?

Question

AcadiFi · Accepted Answer

Rebalancing triggers for immunization balance tracking error against transaction costs. Four common rule frameworks. First, duration drift trigger. Rebalance when portfolio duration deviates from liability duration by more than X% (typically 3-5%) or X years (0.3-0.5 years). For a liability duration of 12.0, rebalance if portfolio falls below 11.5 or rises above 12.5. Duration drifts naturally as time passes (bonds shorten) and as yield curves shift (duration is yield-dependent). Second, rate-move trigger. Rebalance after parallel rate moves exceeding 25-50 bps or KRD-weighted curve shifts above similar threshold. Large moves change reinvestment and price risks asymmetrically; the barbell vs bullet structure may no longer immunize. Third, calendar rebalancing. Monthly, quarterly, or semi-annually regardless of other triggers. This smooths transaction costs and captures the time-decay effect. Most institutional LDI programs rebalance monthly or quarterly. Fourth, event-based rebalancing. Large cash flows (liability payment, new contribution), credit downgrades, or index reconstitution. Example policy for Thornbrook Pension. Rebalance if (a) duration gap exceeds ±0.4 years, OR (b) parallel rate move exceeds 30 bps, OR (c) quarterly calendar, whichever comes first. Execute via a pre-approved list of bonds and futures to cap transaction costs at 5-10 bps per rebalance. Monitor tracking error between portfolio value and liability PV; if cumulative TE exceeds 100 bps, immunization has failed and portfolio requires deeper restructuring. Balance cost: more frequent rebalancing reduces tracking error but transaction costs accumulate. Typical optimal frequency is monthly for large portfolios (low per-unit costs) and quarterly for smaller ones.

What rebalancing triggers should I use for an immunized bond portfolio?

Master Level III with our CFA Course

Related Questions

Practice Questions