Summary of Key Points
This article discusses several “counterintuitive” phenomena in the foreign exchange market in June 2026 (for example, Japan raising interest rates but the yen weakening, and high U.S. inflation leading to a decline in the dollar) to introduce the concept of the “Eurodollar system,” which provides a different perspective on the true nature of the dollar’s movements: A strengthening dollar is not a sign of a strong U.S. economy; rather, it indicates a risk of tightening global dollar liquidity. Conversely, a weakening dollar does not signify the decline of U.S. hegemony but may reflect a relief in liquidity pressures. The article also analyzes how factors such as diverging policies and the sale of reserve assets affect the dollar, correcting common misconceptions about its fluctuations.
Detailed Explanation
1. Why didn’t the yen rise despite Japan raising interest rates by 25 basis points?
In June, the Bank of Japan raised its interest rate to 1% (the highest in 31 years). Logically, raising interest rates should lead to currency appreciation (as it makes saving more attractive), but the dollar appreciated against the yen from 160 to 161.55. The reason is simple: The interest rate differential between the U.S. and Japan is too large, allowing arbitrage transactions to generate substantial profits.
- Arbitrage involves borrowing cheap yen to buy high-yielding dollar assets. For instance, with a yen interest rate of 1% and a dollar interest rate of 3.5%, the difference of 2.5% encourages continued selling of yen for dollars, causing the yen to weaken.
- Japan’s 25-basis-point increase was insignificant in comparison to this large differential, akin to pouring a cup of water into the ocean—too small to change the overall trend. Therefore, even with the rate hike, the yen continued to be sold.
2. Why did the dollar fall despite higher-than-expected U.S. inflation?
In June, U.S. core PCE (inflationary indicator) figures were higher than expected. Traditionally, this would lead the Federal Reserve to raise interest rates and boost the dollar, but instead, the dollar fell by 0.2%. This indicates a shift in market focus:
- Previously, investors focused on the chain reaction of “inflation → rate hikes → dollar gains.” Now, they are more concerned about whether the U.S. economy can withstand further rate increases.
- If economic growth is weak, investors are hesitant to buy dollars (fearing asset depreciation), reducing their attractiveness and causing the dollar to weaken. This signals a shift in market sentiment from defending against inflation to preventing a recession.
3. The Eurodollar system: The hidden driver of dollar movements
To understand dollar fluctuations, one must grasp the concept of Eurodollar—referring not to physical dollars in Europe but to dollar credit outside the United States (such as loans, deposits, and swap transactions between banks worldwide). This system is much larger than the Federal Reserve’s dollar supply and constitutes the primary source of dollars for global trade and corporate financing.
- The liquidity of Eurodollar depends on banks’ willingness to lend. If banks perceive high risks (e.g., market volatility), they may shrink their balance sheets, reducing the availability of dollars and causing the exchange rate to rise; otherwise, it falls.
- To assess the tightness of this system, look at the “cross-currency swap spread.” A higher cost for exchanging euros for dollars (a larger negative spread) indicates greater dollar scarcity. The expansion of this spread in the first half of 2026 signaled a global scramble for dollars.
4. Neither a strong nor weak dollar is necessarily good or bad
The article corrects two common misconceptions:
- A strong dollar does not equate to a strong U.S. economy. For example, during the 2008 financial crisis, despite a struggling U.S. economy, the dollar rose because global banks needed dollars to repay debts and were reluctant to lend, leading to a shortage of dollars.
- A weak dollar does not indicate the decline of U.S. hegemony. For instance, after the U.S.-Iran peace agreement, oil prices fell, reducing the demand for dollars as a safe-haven asset. This was a sign of reduced liquidity pressure, which is a positive development, not a sign of dollar weakness.
5. Diverging global central bank policies make dollar movements more complex
After the “Super Central Bank Week” in June 2026, policies varied:
- Federal Reserve: Hawkish (likely to raise rates but lowered GDP forecasts due to economic concerns)
- European Central Bank: Raised interest rates by 25 basis points and may continue to do so
- Bank of Japan: Raised rates, but the effect was limited, with the yen remaining weak
These divergent policies have increased the tension in the Eurodollar system. Higher U.S. interest rates raise the cost of borrowing dollars, while European rate hikes further tighten liquidity. Japan’s passive rate hike did not reverse the yen’s weakness. Future dollar movements will be more volatile, and investors need to monitor the actions of multiple central banks.
Conclusion
Dollar fluctuations are neither a vote on the greatness of the U.S. economy nor a prediction of its collapse but a reflection of global dollar liquidity. Understanding the Eurodollar system helps avoid being misled by dominant narratives about the decline of U.S. hegemony or the invincibility of the dollar. A strong dollar is often a sign of global dollar scarcity, while a weakening dollar may indicate a relief in liquidity pressures.