Improved subprime performance and a lack of new originations have prompted major nonbank firms involved in subprime servicing to expand their portfolios with acquisitions of nonperforming agency mortgages. Ocwen Financial, Nationstar Mortgage and Walter Investment Management, among others, have all recently acquired large volumes of nonperforming agency mortgages. An estimated $525.0 billion in subprime mortgages were outstanding as of the end of the first quarter of 2012, according to an Inside Nonconforming Markets analysis ... [Includes one data chart]