What is a completion portfolio in fixed income, and how does it fill factor exposure gaps in a multi-manager structure?

A completion portfolio is a dedicated allocation designed to fill the gap between a fund's aggregate factor exposures (from its active managers) and its desired benchmark or liability profile. In fixed income, this typically addresses duration, curve, sector, and credit quality mismatches.

Why Completion Portfolios Exist:

When a plan sponsor hires multiple active bond managers, each manager optimizes their own mandate. The aggregate portfolio often drifts from the benchmark in unintended ways:

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Step-by-Step Construction:

Hargrove Capital manages $3.2B in fixed income across three external managers. The benchmark is Bloomberg US Aggregate.\n\n| Factor | Aggregate | Benchmark | Gap |\n|---|---|---|---|\n| Duration | 6.1y | 7.5y | -1.4y |\n| Spread duration | 4.8y | 4.2y | +0.6y |\n| Govt weight | 18$400M allocation) is constructed to:

1. Add 1.4 years of key rate duration, concentrated in the 10-20 year maturity bucket
2. Reduce net spread duration by holding Treasuries rather than credit
3. Increase government bond weight by ~20 percentage points
4. Offset the MBS overweight by avoiding agency pass-throughs

Implementation Options:

• Passive physical bonds: Buy Treasuries and STRIPS to add duration and government exposure
• Synthetic overlay: Use Treasury futures to add duration and sector exposure without cash
• Semi-active: Allow limited tracking error to add modest alpha while filling gaps
• Dynamic rebalancing: Recalculate gaps quarterly as managers shift exposures

Advantages:

• Preserves each manager's active mandate and alpha potential
• Controls total fund risk at the plan level
• Prevents unintended sector bets from aggregation
• Can be managed internally at low cost

For more on multi-manager structures, check our CFA Fixed Income course materials.