Narendra Modi, the Indian prime minister, rode to power in 2014 with promises to revive economic growth, create jobs for unemployed youth, and find and repatriate money that rich Indians had hidden abroad. Yet change had been incremental.

But on November 8, Mr Modi set off a “big bang” that caught most Indians totally off-guard. In a televised speech, he declared an immediate ban on the use of Rs500 and Rs1,000 notes — 86 per cent of India’s circulating cash supply — in a highly cash-driven economy and ordered that they be returned to banks by the end of the year.

India’s stunned public was told the radical measure would help New Delhi unearth or destroy the illicit wealth that corrupt officials, powerful politicians and tax-dodging businessmen are popularly believed to stash in the form of cash. Indians are now grappling with an unprecedented and highly disruptive experiment, whose outcome will undoubtedly be studied by economists for years to come.