How does currency selection effect work in global fixed income?

Question

AcadiFi · Accepted Answer

Currency selection effect isolates return from active currency allocation in global fixed income, separate from local bond returns and hedging decisions.

Atlas Global Bond Fund currency effect:
- EUR active weight: +10%, EUR return vs USD: +3%
- JPY active weight: -10%, JPY return vs USD: -2%
- EUR contribution: 10% x 3% = +30 bps
- JPY contribution: -10% x -2% = +20 bps
- Total currency effect: +50 bps

The manager correctly overweighted the appreciating currency and underweighted the depreciator.

Decomposition framework (Karnosky-Singer):
1. Market selection (in local currency)
2. Currency selection (pure FX bet)
3. Interaction effect (combined market x currency deviations)

```mermaid
flowchart TD
    A[Total Return Global] --> B[Local Bond Return]
    A --> C[Currency Return]
    A --> D[Interaction]
    C --> E[EUR +30bps]
    C --> F[JPY +20bps]
    E --> G[Currency Effect +50bps]
    F --> G
```

Key methodological points:
- Measure currency returns in base currency terms (USD for Atlas)
- Active weights based on unhedged exposure
- Forward-point adjustments: covered interest parity means hedged returns reflect rate differentials, so hedged currency attribution must be separate
- Cross-currency basis: during stress, deviations from CIP create additional attribution complexity

Hedging treatment:
- Unhedged benchmark + hedged portfolio: attribute hedging P&L as separate line
- Hedged benchmark + unhedged portfolio: portfolio bears currency risk not in benchmark
- Partial hedges: allocate by hedge ratio

Caveats:
- Currency returns include both spot changes and forward premium/discount
- Emerging market currencies may include country-risk premium
- Correlation between local rates and currencies (carry trade dynamics) complicates independent attribution

Skill assessment: currency selection is highly volatile and mean-reverting. A 50bps attribution in one quarter doesn't prove skill — 5+ years of consistent positive currency alpha with low volatility would. Many 'currency managers' actually capture risk premia (carry, value, momentum) rather than discretionary skill.

Atlas's +50bps currency alpha is meaningful this period but needs longitudinal context to establish genuine manager capability versus opportunistic win.

How does currency selection effect work in global fixed income?

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