Quant Memo

FX Carry

Earn the interest rate differential by going long high-yield and short low-yield currencies, with vol scaling.

backtestUpdated 2025-02-12

Thesis (edge)

Currencies with higher interest rates tend to earn carry over time. By going long high-carry and short low-carry, and scaling by volatility, we capture the risk premium while limiting drawdowns.

Where it works (regimes)

Works in risk-on, low-vol regimes. Fails in sudden risk-off (e.g. 2008, March 2020) when carry trades unwind. Use vol targeting and correlation awareness.

Signals

  • Carry = 3m interest rate differential (or forward points).
  • Rank G10 (or EM) currencies; long top 3, short bottom 3 (or long/short spread).
  • Scale by inverse vol (e.g. target 10% portfolio vol).

Portfolio construction

Equal weight or vol-weighted within long and short baskets. Rebalance monthly. Max single-currency exposure.

Risk model

Tail: coordinated unwind. Stress: correlation to equities in crises. Consider trend filter (reduce exposure when trend opposes carry).

Costs & implementation

Moderate turnover. FX spreads and swap costs. Use institutional execution where possible.

Failure modes

Picking up “value trap” currencies (high carry, about to devalue). Ignoring regime.

Our Notes & Suggestions

Combine with simple trend filter (e.g. only hold carry when trend is favorable). Avoid over-concentration in one region. Backtest with realistic FX costs.

Our Notes & Suggestions

See the "Our Notes" subsection in the body above for practical guidance, gotchas, and best practices. Always validate regime assumptions and transaction cost assumptions before scaling.

Implementation Checklist

  • Source 3m forward points or rates
  • Rank currencies by carry; filter by vol
  • Vol-scale position sizes
  • Define max drawdown / deleverage rule

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