Dollar Index Composition and Signals
The U.S. Dollar Index (DXY) measures the dollar against a basket of six major currencies—but the basket is heavily skewed toward Europe. The euro alone comprises 57.6% of the index weight, making DXY essentially a EUR/USD proxy with minor adjustments. Understanding this composition reveals what DXY actually measures and what it misses. The point is: DXY is useful but incomplete. For a full picture of dollar strength, you need to understand its limitations.
DXY Composition: The Six-Currency Basket
The DXY was established in 1973 after the Bretton Woods system collapsed, and its composition hasn't changed since. The weights reflect 1970s-era U.S. trade relationships.
| Currency | Weight | Country/Region |
|---|---|---|
| Euro (EUR) | 57.6% | Eurozone |
| Japanese Yen (JPY) | 13.6% | Japan |
| British Pound (GBP) | 11.9% | United Kingdom |
| Canadian Dollar (CAD) | 9.1% | Canada |
| Swedish Krona (SEK) | 4.2% | Sweden |
| Swiss Franc (CHF) | 3.6% | Switzerland |
Total: 100%
What stands out:
- Euro dominance: More than half the index is one currency
- No emerging markets: China (largest U.S. trading partner) is absent
- European concentration: EUR + GBP + SEK + CHF = 77.3% of the basket
- Legacy composition: Weights haven't been updated in 50+ years
The durable lesson: DXY tells you how the dollar performs against developed-market currencies, primarily Europe. It says nothing about USD strength versus CNY, MXN, KRW, or other major trading partners.
How DXY Is Calculated
DXY uses a geometric weighted average, not a simple arithmetic average. This means percentage changes in each currency pair contribute proportionally to their weights.
The formula:
DXY = 50.14348112 × EUR/USD^(-0.576) × USD/JPY^(0.136) × GBP/USD^(-0.119) × USD/CAD^(0.091) × USD/SEK^(0.042) × USD/CHF^(0.036)
Note the sign conventions:
- EUR/USD and GBP/USD have negative exponents (because these pairs quote USD as the quote currency, not base)
- USD/JPY, USD/CAD, USD/SEK, USD/CHF have positive exponents (USD is base)
Practical interpretation: When DXY rises, the dollar is strengthening against this basket. The 50.14348112 constant was set so that DXY = 100 in March 1973.
Historical Ranges and Levels
DXY has traded in a broad range over its 50-year history:
| Period | DXY Range | Key Driver |
|---|---|---|
| 1973-1980 | 85-105 | Inflation, oil shocks |
| 1980-1985 | 95-165 | Volcker rate hikes (peak: 164.7) |
| 1985-1995 | 80-105 | Plaza Accord, declining rates |
| 1995-2002 | 80-120 | Tech boom, strong U.S. growth |
| 2002-2008 | 72-92 | Housing bubble, low rates (low: 71.3) |
| 2008-2014 | 73-90 | Financial crisis, QE |
| 2014-2020 | 88-103 | Fed normalization, COVID |
| 2020-2024 | 89-114 | Pandemic, hiking cycle (high: 114.8) |
Key reference levels:
- 100: The 1973 baseline; psychological round number
- 90: Support during periods of dollar weakness
- 105: Resistance during mild strength
- 110+: Strong dollar territory; last seen in 2022
- 85 and below: Weak dollar territory; last seen in 2008
The point is: DXY oscillates around 100 over time but can sustain multi-year trends. The 2014-2022 period saw a structural uptrend from 79 to 114.
Trade-Weighted Index vs. DXY: The Differences
The Federal Reserve publishes alternative dollar indices that address DXY's limitations.
Fed Broad Trade-Weighted Index:
- Includes 26 currencies (vs. DXY's 6)
- Weights based on actual trade flows, updated annually
- Includes China (~22%), Mexico (~15%), Canada (~13%)
- Better reflects actual U.S. trade competitiveness
Comparison of weights:
| Currency | DXY Weight | Fed Broad Weight |
|---|---|---|
| EUR | 57.6% | ~18% |
| CNY | 0% | ~22% |
| CAD | 9.1% | ~13% |
| MXN | 0% | ~15% |
| JPY | 13.6% | ~5% |
When they diverge:
- If CNY weakens significantly against USD while EUR stays stable, the Fed index rises more than DXY
- If EUR weakens but EM currencies strengthen, DXY rises while Fed index may be flat
- During EM crises, DXY understates dollar strength
Example divergence (2018 trade war): DXY rose 4% while the Fed Broad index rose 7%, reflecting CNY weakness that DXY missed entirely.
What DXY Strength Signals
A rising DXY carries implications across asset classes:
For equities:
- U.S. multinationals: Earnings headwind (foreign revenue translates to fewer dollars)
- S&P 500: Negative correlation historically (-0.3 to -0.5 correlation with sustained DXY moves)
- Emerging market equities: Stress signal (dollar-denominated debt becomes harder to service)
For fixed income:
- U.S. Treasuries: Mixed (safe-haven flows may support both)
- EM local currency bonds: Negative (currency depreciation erodes returns for USD investors)
- U.S. corporate bonds: Minor impact (mostly hedged issuers)
For commodities:
- Gold: Negative correlation (priced in USD; stronger dollar = lower gold)
- Oil: Negative correlation (same dynamic; 10% DXY move ≈ 5-10% oil move inversely)
- Industrial metals: Negative (demand from EM, priced in USD)
Signal interpretation framework:
| DXY Move | Signal | Portfolio Implication |
|---|---|---|
| Rising above 105 | Risk-off environment strengthening | Reduce EM exposure, watch multinational earnings |
| Falling below 95 | Risk-on, global growth favored | Increase international allocation |
| Breaking 110+ | Stress conditions, flight to safety | Defensive positioning, quality focus |
| Stable 95-105 | Neutral environment | Focus on fundamentals, not currency |
Correlation with Risk Assets
DXY tends to strengthen during risk-off episodes and weaken during risk-on periods. This relationship isn't perfect but is persistent enough to inform allocation decisions.
Historical correlation examples:
- March 2020 COVID crash: DXY spiked from 95 to 103 as markets panicked
- 2022 Fed hiking cycle: DXY rose from 96 to 114 as rates rose and risk appetite fell
- 2023 recovery: DXY declined from 114 to 101 as recession fears faded
The mechanism:
- Risk-off triggers: Investors sell risky assets
- Capital flows to U.S.: Dollar demand increases
- DXY rises: Basket currencies weaken vs. USD
- Feedback loop: EM stress from stronger dollar creates more risk-off
A → B → C chain:
Risk-off event → USD demand surge → DXY spike → EM pressure → Additional risk-off
The point is: DXY is both a signal and an amplifier. Strong dollar conditions create stress in dollar-indebted economies, which creates more dollar demand.
Limitations and Misinterpretations
Limitation 1: Euro dependence
A 2% EUR/USD move shifts DXY by approximately 1.15% (57.6% weight). Meanwhile, a 2% move in USD/CAD shifts DXY by only 0.18%. DXY can miss significant dollar movements against non-EUR currencies.
Limitation 2: No China
China is the largest U.S. trading partner, but CNY isn't in DXY. During CNY depreciation episodes, DXY understates actual dollar strength.
Limitation 3: Legacy weights
Sweden (0.4% of U.S. trade) has more weight than Mexico (15% of U.S. trade). The index reflects 1973 trade patterns, not today's reality.
Misinterpretation 1: "DXY at 100 means the dollar is neutral"
The 100 level is an arbitrary 1973 baseline. It has no fundamental meaning for current valuations.
Misinterpretation 2: "DXY rising means all foreign investments will underperform"
DXY doesn't include EM currencies. Strong dollar conditions affect EM more than DM, but DXY may not capture that.
Detection Signals: You're Likely Misjudging DXY If...
- You're using DXY to gauge USD/CNY or USD/MXN exposure (these aren't in the index)
- You assume DXY moves perfectly correlate with S&P 500 moves (correlation is moderate, not tight)
- You treat DXY = 100 as a "fair value" level (it's just a baseline)
- You're overweighting DXY for EM allocation decisions (use Fed Broad index instead)
- You ignore that a single EUR/USD move drives most DXY action
Checklist: Using DXY Effectively
Essential (for basic monitoring)
- Know the six components and their weights
- Track DXY alongside EUR/USD (they move together)
- Compare DXY to Fed Trade-Weighted Index for divergences
- Identify current DXY level relative to 90-110 range
High-Impact (for portfolio decisions)
- Monitor DXY alongside risk sentiment indicators (VIX, credit spreads)
- Adjust multinational earnings expectations for sustained DXY moves
- Use Fed Broad index for EM allocation decisions
- Track DXY breakouts from range as regime change signals
Your Next Step
Compare DXY to the Fed Broad Trade-Weighted Index over the past year. Identify periods where they diverged significantly and research what caused the divergence (likely CNY or MXN moves). This exercise reveals when DXY misleads and when you need broader measures.
Where to find data:
- DXY: Yahoo Finance (DX-Y.NYB), ICE Exchange
- Fed Broad Index: Federal Reserve FRED database (TWEXBGSMTH)
Related: How Exchange Rates Are Quoted | Interest Rate Differentials and Carry | Macro Drivers of USD Strength or Weakness
Sources: ICE Futures U.S. (2024). U.S. Dollar Index Methodology. | Federal Reserve Board (2024). Trade-Weighted Dollar Index Documentation.