Freddie Mac announced its fifth Structured Agency Credit Risk debt note offering in 2015 this week. This $950 million offering comes on the heels of last week’s STACR offering of $425.6 million, which was the first transaction under a new structure that shares a reference pool of loans with a previous transaction.Last week’s STACR Series 2015-HQ2 has a reference pool of single-family mortgages with an unpaid principal balance of more than $30.3 billion. Freddie said the reference pool consists of a subset of 30-year fixed-rate single-family mortgages acquired by Freddie in the first through third quarters of 2013 with loan-to-value ratios from 80 to 95 percent. Analysts from Moody’s Investors Service said Freddie used part of its 58 percent....