Overseas investors emerged as one of the surprise developments of the 2004 MBS market, and they are likely to continue increasing demand and driving spreads tighter this year, according to Bear Stearns analysts. “In 2004, the mortgage market found a new sponsor, and she lives overseas,” wrote Bear Stearns analysts Steven Abrahams and Adam Rilander in a new market overview. “China found itself with a quickly growing dollar portfolio and put increasing amounts of that…