What it means
Currency correlations measure how FX pairs move together over a given window. EUR/USD, GBP/USD, AUD/USD and NZD/USD share the USD leg, so positive correlations of 0.6-0.9 are typical. Commodity currencies (AUD, CAD, NZD) correlate with risk-on assets and inversely with safe havens (JPY, CHF). Correlations shift across regimes — risk-off periods compress correlations toward ±1 as 'sell everything' takes over.
Why it matters
Multi-pair positions assumed to be independent are usually one trade in disguise. Long EUR/USD + long GBP/USD + long AUD/USD is effectively 'short USD' three times. If USD strengthens unexpectedly, all three lose simultaneously — the diversification you thought you had isn't real.
How to use it
Compute rolling 30-day correlations across your active pairs. For risk budgeting, treat highly-correlated positions (|ρ| > 0.7) as a single thesis with shared risk. For pairs trading, look for normally-correlated pairs that have momentarily de-correlated as mean-reversion opportunities.
30-day correlation: EUR/USD vs GBP/USD = 0.82, EUR/USD vs USD/JPY = -0.64, EUR/USD vs AUD/USD = 0.71. A 1% USD rally moves all four pairs roughly the same magnitude in their respective directions — they are not four independent trades.
Want a worked example or a deeper dive? Ask Rocky how this concept applies to your specific watchlist or trade idea.
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