In this new era of rampaging oligarchs, nothing may seem as satisfying as slapping a tax on Elon Musk’s new trillion-dollar fortune. What most bothers Americans about federal taxes is that billionaires don’t pay their fair share. As the race to develop artificial intelligence mints more billionaires, policymakers’ temptation to directly tax their brobdingnagian wealth is becoming unbearable.

The first state out of the blocks is California, where voters in November will decide whether to impose a one-time tax of 5% on fortunes worth more than $1bn. Given the ease with which plutocrats avoid paying income taxes, the case for this sort of direct tax on their stash appears unassailable.