BOFA GLOBAL RESEARCH FX & RATES STRATEGY BRIEFING: EQUITY BREADTH & THE US DOLLAR

THE TAKE: EQUITY BREADTH IS A STATISTICALLY SIGNIFICANT USD DRIVER

Bank of America Rates & Currencies Research demonstrates that US equity market breadth is a statistically significant, independent driver of the US Dollar Index (DXY), operating beyond traditional equity index levels and 2-Year Treasury yield differentials. Equity breadth serves as an empirical barometer of US Technology Exceptionalism vs. Global Growth Convergence:

  • Narrow Rally / Broad Sell-Off = USD Positive: When S&P 500 performance is concentrated in mega-cap technology while the broader market lags (i.e., S&P 500 equal-weighted SPW underperforms SPX), capital concentrates into US tech, supporting the Dollar.

  • Broad Rally / Narrow Sell-Off = USD Negative: A broader market advance or a localized sell-off in mega-cap tech signals global growth convergence or an erosion of US AI exceptionalism, weighing on the Dollar.

  • October Market Read-Through: The stable-to-weaker USD during October’s equity drawdown aligns with AI debt and capex concerns undermining the US exceptionalism narrative.

REGRESSION BETA BREAKDOWN & SCENARIO ANALYSIS

BofA strategists regressed weekly FX returns since 2015 against the relative performance of equal-weighted S&P 500 (SPW) vs. cap-weighted S&P 500 (SPX), controlling for 2-Year US Treasury rates and S&P 500 index moves:

  • DXY Sensitivity: A 1% rise in SPW vs. SPX (improving breadth) is associated with a -0.2% depreciation in the DXY Dollar Index.

  • Cyclical FX High Betas: The most cyclical, high-beta currencies—specifically the Nordics (SEK, NOK) and Antipodeans (AUD, NZD)—display the highest statistical sensitivity to equity breadth, reinforcing the global growth read-through.

  • EUR/USD Breadth Sensitivity: For EUR/USD, the equity breadth sensitivity exceeds standard equity level sensitivity, making SPW/SPX performance a critical input for Euro positioning.

  • Japanese Yen (JPY) Exception: JPY is the sole currency outlier where the equity breadth beta is not statistically significant. Japan's foreign asset structure (skewed toward FDI rather than portfolio flows) means front-end US yields—rather than equity risk sentiment—dominate USD/JPY directional moves.

ILLUSTRATIVE MARKET SCENARIOS

  1. Broadening Rally Scenario: Both equity level and breadth effects act in tandem to depress the USD, driving strong outperformance in high-beta and cyclical currencies.

  2. Tech-Led Equity Correction (10% SPX Drop with 6% SPW Outperformance): The positive USD impact from falling equity index levels is neutralized by the negative USD impact of improving relative breadth (SPW > SPX). DXY remains broadly net-neutral.

  3. Rates Channel Dominance in Equity Pullbacks:

    • Driven by US Growth Scares / Lower Front-End Yields: Favors long JPY and CHF positions over USD.

    • Driven by Higher Treasury Yields (2022 Style): Broadly USD positive across the board.

Source Document: BofA Global Research (Adarsh Sinha, Oliver Levingston)