日元為何成為全球最弱主要貨幣：一堂貨幣政策分歧課

In mid-2026, the Japanese yen has been labeled the "world's weakest major currency," depreciating to levels not seen since the 1980s against the US dollar. The decline is not a sudden crisis but the result of a fundamental monetary policy divergence that has been building for years.

Knowledge point: the interest rate differential engine

Currency values are driven by many factors, but the most powerful short-to-medium-term driver is the interest rate differential between two countries. When the US Federal Reserve raised rates aggressively to fight inflation (taking the federal funds rate above 5%), the Bank of Japan maintained its ultra-loose policy with rates near zero. This created a massive gap: investors can borrow yen at near-zero cost and invest in dollar-denominated assets yielding 4-5%. This is the "carry trade," and it creates relentless selling pressure on the yen.

The BOJ has attempted modest rate hikes, but the gap remains wide. Japan's economy also faces structural headwinds: an aging population, high government debt (over 250% of GDP), and persistent deflationary psychology that makes aggressive tightening risky.

Who wins and who loses

A weak yen is a double-edged sword. Japanese exporters — automakers, electronics firms — benefit because their products become cheaper abroad and overseas earnings are worth more when converted back to yen. Tourism booms as Japan becomes a bargain destination. But importers, households, and small businesses suffer: energy, food, and raw materials all become more expensive. Japan imports nearly all of its oil and gas, so a weak yen directly raises living costs. The knowledge lesson: exchange rates are not simply "good" or "bad" — they redistribute benefits and costs across different segments of the economy.