Originators of alternative mortgages are pooling a growing amount of their production in securities programs designed for prime jumbo loans, resulting in a witch’s brew of products known as “prime mix” MBS. According to an analysis by Inside Alternative Mortgages, $44.44 billion in prime mix pools – or prime non-agency MBS pools that contain at least 35 percent conforming balance loans – were issued during the first six months of the year. Issuance was heaviest in... [One data table included]