Two months ago Japan?s central bank, which for years had been battling against deflation, finally flicked off the switch marked ?free money?.

Since then, the oceans of cash it had been pouring into the financial system have been dwindling. In just nine weeks, liquidity has halved to about Y15,000bn ($135bn, ?106bn, ?72bn). At this rate, by early June, the Bank of Japan?s measure of liquidity ? current account balances kept at the bank ? will have dropped to about Y8,000bn. Below this level, overnight interest rates will start flickering above zero as demand for overnight money outstrips supply.