Freddie Mac made a move this month to bolster its presence in the alternative-mortgage market by improving the transparency of its pools of adjustable-rate loans. According to a released statement, Freddie said five new data fields will be added to the Participation Certificates backed by adjustable-rate mortgages starting in September. These data elements are already available for fixed-rate loans, and should help investors better identify the rates of prepayment on various mortgage-backed securities. …