In 2015, Clyde Prestowitz’s book Japan Restored imagined a Japanese century emerging from upheavals such as an Israeli attack on Iran. While conflict now grips the Middle East, there are few indications of the revolutionary change the former US national security official foresaw. But in one crucial respect this already is a Japanese century – thanks to the yen’s role as easy money for global finance.

The Bank of Japan’s loose monetary policy has turned the yen into the world’s cheapest and most reliable funding currency. By suppressing yields on public debt to keep Japan’s domestic economy afloat, the BoJ effectively created a publicly subsidised funding pipeline for bankers. They can make a quick buck by borrowing cheaply in yen and investing in higher-return assets, such as US equities. The “yen carry trade” surged after the........

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