Currency linkages

Definition

Currency linkages are the paths by which exchange rates — especially the US dollar — transmit into equity, commodity, and rate positions: translation (foreign revenues and holdings convert at the rate — instrument-adr decomposition), competitiveness (a strong dollar squeezes US exporters and EM dollar-borrowers), and denomination (dollar-priced commodities move inversely with the dollar, mechanically and behaviorally). A US-listed portfolio is short-dollar-exposure in more places than its tickers suggest.

How it works / structure

• State variables (engine-executable): broad dollar index level and trend (DXY or the Fed’s broad index — pinned), rate differentials (the carry structure — strategy-futures-carry FX section, ext-fx for the market itself), and dollar-liquidity stress gauges (the dollar spikes in global stress — the flight-to-dollar pattern documented across crises).
• Documented transmissions: S&P 500 constituents derive roughly 30-40% of revenues abroad (per S&P/FactSet aggregations — level varies by year and sector) — dollar strength is an earnings headwind with sector concentration (tech and industrials most exposed); commodities priced in dollars show negative dollar correlation (macro-commodity-linkages); EM equities carry a documented dollar-funding sensitivity.
• The forecasting humility: Meese-Rogoff (1983) — the canonical result that exchange-rate models failed to beat a random walk out of sample at short horizons — still broadly stands; the platform treats currency LEVELS as untradeable forecasts and currency EXPOSURE as measurable fact.

When it applies

Attribution and exposure accounting (the FX leg of ADRs and international ETFs decomposed, hedged-vs-unhedged share classes chosen consciously — ext-international-equities); earnings-season dollar theses on exposed sectors; commodity positions’ dollar overlay; stress positioning (dollar-up is part of the crisis correlation set, risk-correlation-exposure).

Risk profile & failure modes

• Invisible exposure: unhedged international holdings and multinational earnings carry FX risk the position labels hide; attribution without the FX leg mis-credits skill.
• Forecast hubris: rate differentials, PPP, and current accounts all fail as short-horizon predictors (the Meese-Rogoff legacy) — dollar theses need event or flow mechanisms, not equilibrium stories.
• Correlation instability: the dollar-commodity and dollar-equity correlations vary by driver (growth vs stress vs policy divergence) — sign lore without the driver stated is unreliable.
• Hedging costs: FX-hedged share classes pay the rate differential; hedging a high-carry currency exposure has a running cost the label omits.

Evidence & limits

Market structure and turnover are BIS-documented; the revenue-exposure aggregates are index-provider data (levels quoted as approximate and year-dependent); Meese-Rogoff (1983) anchors the forecasting humility and its qualified survival is part of the exchange-rate literature’s core. Transmission CHANNELS are well documented; tradeable short-horizon currency prediction is not.

Falsifiable-thesis examples

Illustrations only, not signals:

• “If the broad dollar index rises 5%+ this quarter, the high-foreign-revenue decile of the S&P will underperform the domestic-revenue decile” — falsified by the conditional pair.
• “X-ADR’s USD return this year will decompose to more than half FX (translation-dominance thesis)” — falsified by the decomposition.

Cross-references

• The market itself: ext-fx; carry economics: strategy-futures-carry
• Exposure carriers: instrument-adr, ext-international-equities, macro-commodity-linkages
• Stress behavior: risk-correlation-exposure, regime-volatility