Just as the ‘poverty line’ determines what’s required for basic living, we need a ‘wealth line’ to show when extreme wealth becomes harmful

It was bound to happen eventually: Elon Musk has become the planet’s first trillionaire. Until recently, economists who spoke about “trillions” were describing the GDP of the largest economies or the accumulated value of bequests on their way to the heirs of today’s billionaires. The term is not often used in daily conversation, let alone to describe the wealth of an individual.

But now we have entered a new phase of the oligarchic era. Previously, when we described the wealth of the world’s richest billionaires, it was understood as a few hundred billions. Three years ago, the value of Musk’s total assets was estimated to be about $250bn. The pace at which it has increased is mind-boggling – and so is what it represents.