Freddie Mac released its monthly-volume summary report Friday, and it shows the aggregrate unpaid principal balance of the GSE's mortgage-related investments portfolio declining by $5.7 billion in December.

Yet, the company’s total mortgage portfolio still edged up at an annualized rate of 0.4% in December.

Single-family refinance loan purchase and guarantee volumes hit $10.8 billion in December, representing 50% of total single-family mortgage portfolio purchases or issuances.

"Relief refinance mortgage comprised approximately 29% of our single-family refinance volume during December 2013 based on unpaid principal balance," the monthly summary volume report says.

The GSE’s single-family seriously delinquency rate fell from 2.43% in November to 2.39% in December, while the multifamily delinquency rate increased from 0.05% in November to 0.09% in December.

New multifamily business activity reached $3.7 billion in December and $25.9 billion for the 12-month period ending Dec. 31, 2013.

The total number of loan modifications at Freddie hit 6,731 in December, and 83,188 for the 12-month period ending in December.