A Basket Carry Strategy: Diversifying the Interest Differential

[Fairman]

A Basket Carry Strategy: Diversifying the Interest Differential

A single carry trade is exposed to one currency's risk. A basket carry strategy spreads exposure across several pairs, which smooths the ride.

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The construction is straightforward. Rank a group of liquid currencies by their short-term interest rates. Go long the several currencies with the highest rates, and short the several with the lowest, in roughly equal risk terms. Rebalance periodically, such as monthly or quarterly, as rates change.

The expected return is the interest differential, plus or minus the exchange rate changes. Academic research has found that carry strategies earned positive average returns over long periods, which is often explained as compensation for crash risk.

That risk is real. Carry baskets tend to deliver steady gains punctuated by sharp losses when risk appetite collapses and high-yielding currencies fall. The period around 2008 saw large drawdowns.

Practical issues also arise. Retail swap rates include broker markups, which reduce the carry. Position sizing needs to account for the volatility of each currency, not just equal lots. Margin and costs for multiple positions add up.

Risk controls help: limit total exposure, use stops or volatility filters that reduce positions when volatility spikes, and avoid concentrating in exotic currencies with large tail risk.

Test the strategy including realistic swap values, since the headline interest differential overstates what you receive.

Practical step: compute the net swap on a basket of four pairs on your platform, and compare with the theoretical interest differential.

[Fairman]

The net swap check is where this usually gets humbling. After broker markups, the carry you actually receive on a retail account can be a fraction of the textbook differential. Before building a basket, list each pair you'd hold, the long or short swap your broker pays in points, and convert it to an annual percentage of the position. Compare that with the interest rate gap between the two countries. If the broker is keeping half or more, the strategy's expected return shrinks a lot, while the crash risk stays exactly the same. Some brokers are much better than others on this, so it's worth comparing a few before committing.

[Fairman]

Volatility sizing is the part people skip. Equal lots across a basket means the most volatile currency quietly dominates your risk, and that's usually the one that crashes in risk off. For example, if you hold equal lots in AUDJPY, NZDJPY and USDMXN, the peso position may swing much more than the others in money terms. A simple fix is to size each position so that one ATR move is worth roughly the same amount in your account currency. That way each leg contributes similar risk. It doesn't remove the crash risk, since they can all fall together, but it stops one pair from deciding the result of the whole basket.