The U.S. financial markets may have been closed due to the Martin Luther King Jr. Day observance, but stock markets around the world tumbled as worries over the U.S. economy took hold. Johan Stein, who manages about $14 billion at an asset management firm in Stockholm told Bloomberg, "It's the worst I've ever seen. The financial system is in terrible shape, and no one knows where this will end.'' Many investors are doubtful that President......