Subprime loans became a more prominent part of the mortgage market last year, when a surge in originations helped servicers add a significant volume of new business to their books. According to a new ranking and analysis by Inside B&C Lending, the total volume of subprime loans outstanding rose 39.1 percent in 2004, to $973.2 billion. Outstanding volume rose by 9.7 percent between the third and fourth quarter, with $85.7 billion in new loans…