The yen has been falling primarily because of simple economic logic. The gap in interest rates between Japan and America is yawning. Although the Bank of Japan raised rates in February, it did so by only a smidgen: they increased from between minus 0.1% and zero to between zero and 0.1%. Rates in booming America, by contrast, are more than five percentage points higher. It is easy for investors to lose a fortune in the financial markets and even easier for governments. In 2022 Japan spent more than $60bn of its foreign-exchange reserves defending the yen, its first intervention to strengthen the currency in nearly a quarter of a century. Is it the right thing to prop up the Yen?

