Despite a slight year-over-year increase in mortgage purchases and issuances, Freddie Mac’s total mortgage portfolio continued to shrink in April, according to the organization’s Monthly Volume Summary.

The summary, released Friday, showed that the corporation’s total mortgage portfolio decreased at an annualized rate of 14.1 percent, much higher than March’s rate of 2.9 percent and April 2011’s 3.2 percent. The portfolio’s negative annualized growth rate to date in 2012 is 6.2 percent.

This news comes in spite of April’s total of issuances and purchases: $25.9 billion, an increase from the previous year’s total of $23.8 billion. The difference in year-over-year totals came from a much larger number of liquidations – $47.3 billion in April 2012 compared to last year’s $28.1 billion.

The ending balance for April’s total mortgage portfolio was $2.03 trillion, down more than $20 billion from March and more than $100 billion year-over-year.

Also of note was this year’s mortgage-related investments portfolio, which has a year-to-date negative growth rate of 23.8 percent.

The portfolio shrank at a rate of 32.6 percent, another huge year-over-year rate increase from 9.2 percent in April 2011.

Mortgage-related purchases were only $1.8 billion this year, a major drop from last year’s $12.3 billion. The aggregate unpaid balance of the portfolio was approximately $16.8 billion.

All the components of Freddie Mac’s mortgage-related portfolio decreased month-to-month and year-over-year, leading to an ending balance of approximately $601 billion and continuing the monthly drop.

Mortgage-related securities and other guarantee commitments also shrank in April at a rate of 9.2 percent, a turn down from the February and March’s upward growth.

Single-family refinance-loan purchases and guarantee volume was $19.1 billion, nearly three-quarters of total mortgage portfolio purchases and issuances.

The single-family seriously delinquent (90-plus days) rate stayed at 3.51 percent while the multifamily delinquency rate increased a small amount to 0.25 percent.

Freddie Mac’s total number of loan modifications in April 3,454, bringing the year-to-date total to 17,131.