FAQs: Agency MBS CUSIP Aggregation

The following frequently asked questions (FAQs) provide further information about the Federal Reserve Bank of New York's (New York Fed) plans to consolidate certain agency mortgage-backed securities (MBS) that are held in the System Open Market Account (SOMA) through a process called CUSIP aggregation.

Effective November 16, 2020


What is a CUSIP?
A CUSIP is a unique security identifier developed by the Committee on Uniform Security Identification Procedures.

What is CUSIP aggregation?
Agency MBS CUSIP aggregation is a process through which a number of existing MBS CUSIPs issued or guaranteed by Fannie Mae, Freddie Mac, or Ginnie Mae (agency MBS) with similar characteristics, such as coupon and original term to maturity, are consolidated into a larger pass-through security. The aggregated CUSIP securities are similar to those agency MBS being consolidated, except that the aggregated securities represent groups of agency MBS, which themselves represent groups of residential mortgages that conform to specified requirements. The cash flows from the underlying agency MBS provide the cash flows for the new aggregated CUSIP so the overall size and characteristics of the SOMA MBS portfolio remain unchanged. This aggregation service is offered by Fannie Mae, Freddie Mac, and Ginnie Mae.

What are the benefits of CUSIP aggregation?
CUSIP aggregation is commonly used by market participants to more efficiently manage agency MBS portfolios. Specifically, CUSIP aggregation simplifies back-office operations and reduces operational risks and administrative costs associated with holding a large number of individual agency MBS CUSIPs.

The Federal Reserve has previously engaged in CUSIP aggregation, including two rounds of Fannie Mae and Freddie Mac aggregations which began in 2011 and 2015, and one round of Ginnie Mae aggregation which began in 2019.  Together, these aggregation programs have reduced the number of individual CUSIPs in the SOMA portfolio by over 100,000.

Does CUSIP aggregation imply anything about the Federal Reserve’s future plans related to agency MBS holdings or broader monetary policy actions?
No. CUSIP aggregation is a matter of prudent portfolio administration by the New York Fed, and no inference should be drawn about the timing or nature of any future plans related to the Federal Reserve’s agency MBS portfolio or broader monetary policy actions.

Will CUSIP aggregation interfere with Federal Reserve purchases of agency MBS?
No. CUSIP aggregation and purchases can be conducted simultaneously.

Will CUSIP aggregation affect any of the characteristics associated with the SOMA’s agency MBS portfolio?
No. Cash flows on the underlying agency MBS flow through to the aggregated CUSIPs, so CUSIP aggregation will not affect the size or characteristics of the SOMA portfolio.

How will the Single Security Initiative impact the Desk's CUSIP aggregation strategy?
The Single Security Initiative allows agency MBS holders to combine Fannie Mae Uniform MBS (UMBS) and Freddie Mac UMBS together provided they have the same coupon, term to maturity and 55-day payment delay. The Desk will combine eligible Fannie Mae UMBS and Freddie Mac UMBS together according to the filtering methodology described below, where appropriate. Legacy Freddie Mac MBS with a 45-day payment delay, commonly known as Freddie Mac PCs, will continue to be aggregated separately from UMBS.


What is the Desk’s CUSIP aggregation strategy?

Fannie Mae and Freddie Mac

For Fannie Mae and Freddie Mac MBS, the Desk will filter along five criteria: Pool category, year produced, security type (UMBS or legacy Freddie Mac PCs), coupon, and original term to maturity. Pools backed by mortgages issued in Puerto Rico are first separated out from the rest of the portfolio, followed by pools with lower original loan balances and then by pools backed by mortgages issued in the state of New York. These types of pools are commonly referred to as “story pools” in the agency MBS market.  These three story pool categories are handled separately from “no story pools,” which are those pools that do not qualify for any of the three story pool categories. The majority of SOMA holdings fall into the no-story-pool category.

Both story and no story pools are then filtered into cohorts by security type (UMBS or legacy Freddie Mac PCs), coupon, original term to maturity and year produced. Older cohorts are grouped together while newer cohorts are typically separated by year. For certain cohorts where holdings are relatively low, pools are aggregated together by security type and coupon only.  Once the filtering process is complete, cohorts will be aggregated as long as they contain at least 10 underlying CUSIPs.

Any aggregated CUSIPs that do not meet the requirements described above may be created, when appropriate, using a less stringent filtering scheme. The resulting aggregations could be less homogenous than those created in the strategic aggregation process, but nonetheless help consolidate the portfolio and reduce administrative costs. 

Ginnie Mae

For Ginnie Mae MBS, the Desk’s aggregation program included only securities issued under the Ginnie Mae I program. Ginnie Mae II securities, on the other hand, were excluded from the aggregation program given that they are securitized in such a way as to minimize the need for aggregation. In addition, story pools – including pools backed by mortgages issued in Puerto Rico and New York, and pools with lower original loan balances – were also excluded from the Ginnie Mae aggregation program. 

The remaining no story pools, which make up the majority of SOMA Ginnie Mae I holdings, were filtered by coupon and vintage. In contrast to Fannie Mae and Freddie Mac aggregations, most of these pools were then grouped together and aggregated based only on their coupon.  For example, all no story vintages of 30-year Ginnie Mae I securities with a 3.5 percent coupon were aggregated into a single CUSIP.

The Ginnie Mae CUSIP aggregation program began in March 2019 and was completed in July 2019 and the Desk consolidated approximately 8,000 individual CUSIPs into about 8 aggregated ones.

What were the key considerations in determining the Desk’s strategy?
The aggregation process was designed to reduce administrative costs and operational complexities associated with the Federal Reserve’s agency MBS portfolio using a straightforward and rules-based approach that is consistent with market functioning objectives and standard market practices. The Desk’s CUSIP aggregation strategy as described above may be modified, as needed, over time.


How will the public be informed of aggregated agency MBS holdings?
The New York Fed publishes detailed data on all settled SOMA agency MBS holdings on its public website on a weekly basis.

In addition, Fannie Mae, Freddie Mac, and Ginnie Mae provide information about aggregated CUSIPs, including the underlying agency MBS, on their public websites.

Will information about the agency MBS underlying the Federal Reserve’s aggregated CUSIPs remain available to the public?
Yes. Information about individual Fannie Mae, Freddie Mac, and Ginnie Mae agency MBS CUSIPs underlying the Federal Reserve’s aggregated CUSIPs will remain available on these organizations' public websites.

FAQ: August 30, 2019 »

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