Japan became the biggest overseas investor in U.S. MBS and ABS markets last year, moving past mainland China to head the ranking, according to final Treasury Department data. Japanese investors held $199.7 billion of U.S. MBS and ABS as of the midway point in 2012, the one time a year when Treasury releases detailed foreign holdings of U.S. long-term securities. That was up 21.3 percent from June 2011, when Japan held just $164.7 billion of MBS and ABS. The Japanese increased...[Includes one data chart]