Led by market leader Bharti Airtel, Indian telecom crossed an invisible line in October 2008. For the first time in the country, a telecom market—Delhi—had more mobile subscriptions than people. Nineteen million subscriptions for a 17 million-strong population.

The crossing of that invisible line in Delhi was soon followed by many other cities. Chennai, six months later. Then Mumbai and Kolkata by November 2009.

After rightly attributing 100-plus percent mobile penetration to the rise of customers using multiple SIMs, Sanjay Kapoor, the CEO of Bharti Airtel at the time, was still upbeat, saying, “As an operator, we see the SIM penetration going up further as new applications come in.”

But in October 2018, exactly a decade after Delhi crossed 100% mobile penetration, Gopal Vittal, Kapoor’s successor, did the unthinkable.