Exponentiality often has unexpected effects. Take chewing gum. In the 10 years from 2007, American chewing gum sales fell 15 per cent – just as 220 million American adults bought their first smartphone. This was no coincidence. When people got into a shop queue, they would once have spent the time browsing the goodies for sale at the counter – and gum was the obvious choice. Now they were spending that time playing with their phones. So gum sales plummeted.
