First Republic Bank was the top contributor to jumbo mortgage-backed securities through the first three quarters in 2013, according to a new ranking and analysis by Inside Nonconforming Markets. Meanwhile, underwriting trends for the sector were mixed. Some $2.10 billion in originations by First Republic were included in jumbo MBS this year, as of the end of September. The loans accounted for 17.2 percent of all non-agency jumbos securitized, more than double the next closest lender ... [Includes two data charts]