This year, Nouriel Roubini, the economist known to the general public as Dr. Doom, Prophet of the Financial Apocalypse, spent the early hours of Mardi Gras on the floor of the Frankfurt Stock Exchange. It was only 11 a.m., but the party was rollicking. Traders careened around the floor, hooting and honking, dressed as dragons and devils and convicts. Rock music roared overhead, and no one seemed to care that, by the bye, the market had tanked. Tickled, Roubini registered the flicker of amusement on his Twitter thread: "Nouriel is at the Frankfurt Stock Exchange," he wrote, "where everyone is dressed in Mardi Gras costumes even if the market is down 2.5%."