Two banks dominated contributions to prime non-agency mortgage-backed securities issued in the past two years, according to a new ranking and analysis by Inside Nonconforming Markets. And a majority of the top 10 contributors to prime jumbo MBS were banks or affiliated with banks. JPMorgan Chase accounted for $4.58 billion of the prime mortgages included in prime non-agency MBS in 2015 and 2016, a 22.1 percent share of total issuance ... [Includes one data chart]