“The astronomical rise in prices for the most-sought-after works of art over the last generation is in large part the story of rising global inequality. At its core, this is the simplest of economic math. The supply of Picasso paintings or Giacometti sculptures (one of which sold for $141 million in the same auction this week) is fixed. But the number of people with the will and the resources to buy top-end art is rising, thanks to the distribution of extreme wealth.”