The Freddie Mac delinquency rate increased 1 basis point in July to 3.51%, the first increase since November. The rate is a percentage of the mortgages backing securities Freddie Mac guarantees. Freddie cut its guarantee book every month since February 2010. It dropped below $1.7 trillion in July, a $9 billion reduction from the previous month and the lowest point since October 2007, according to the Freddie monthly summary. “The falling denominator is a principal reason the serious delinquency percentage ticked up during the month,” said Jim Vogel of FTN Financial. A spokesperson for Freddie said there was also a slight uptick in seriously delinquent loans, but it was nearly offset by a dip in delinquent mortgages transitioning to REO. New Freddie Mac purchases and issuance dropped to $20.7 billion in July, the lowest monthly amount since October 2008. Freddie also continued to cut its retained mortgage investment portfolio as required under its conservatorship agreement. The Treasury Department capped this portfolio at $900 billion at the end of 2009 and scheduled it to be wound down by 10% each year, reaching $250 billion by 2018. Freddie remains on schedule, reducing the portfolio to $683 billion as of July, down roughly $2 billion from the previous month and more than $40 billion from one year ago. Write to Jon Prior. Follow him on Twitter @JonAPrior