The extraordinary three-day auction of the Yves Saint Laurent-Pierre Bergé collection has put the global art market in an entirely new perspective. It has finally demonstrated that the art market is set on a separate trajectory from the rest of the world economy and, even more importantly, it has altered the international power balance on the auction scene. To the general public, the string of world auction records set this week, from 20th-century paintings to Old Masters to Art Deco furniture, is the most striking evidence that the art market is performing beautifully. The sale, conducted by Christie's, took in...