Paul Krugman is retiring as a columnist for the New York Times, according to a Friday statement from Opinion Editor Kathleen Kingsbury, who called his 25-year tenure “a ride at The Times worthy of the best bull market.” Her full statement is below: I want to take you back to Jan. 2, 2000, a day when Y2K was in the rearview mirror and the dot-com bubble burst was just around the corner, when the Dow stood at a mighty 11,500 and a New York Times Opinion columnist debuted on the scene with the first of many prescient arguments and ideas...