Agency MBS: Ginnie Mae, Fannie Mae & Freddie Mac

What Are Agency MBS?

Agency MBS are mortgage-backed securities that are issued or guaranteed by one of three U.S. government-affiliated entities: the Government National Mortgage Association (Ginnie Mae), the Federal National Mortgage Association (Fannie Mae), and the Federal Home Loan Mortgage Corporation (Freddie Mac). These three organizations sit at the center of the American housing finance system, and the agency MBS they create represent one of the largest and most important asset classes in global capital markets.

The mechanism is straightforward in concept. Thousands of individual residential mortgages are pooled together into a single security. Investors who purchase that security receive monthly payments derived from the mortgage payments made by the underlying homeowners. The agency that issues or guarantees the MBS absorbs the credit risk: if a homeowner defaults, the agency ensures that investors continue to receive their scheduled principal and interest payments.

This credit guarantee is what distinguishes agency MBS from the broader universe of mortgage-backed securities. Non-agency or “private label” MBS, which are issued by banks and other financial institutions without a government guarantee, carry the credit risk of the underlying mortgage pool directly. Agency MBS effectively eliminate credit risk from the investor's perspective, leaving interest rate risk and prepayment risk as the primary sources of return variability.

With approximately $9.5 trillion in outstanding securities, agency MBS constitute roughly 75% of the total U.S. MBS market and represent the second-largest fixed-income market after U.S. Treasuries.

The Three Agencies: Roles and Distinctions

Although Ginnie Mae, Fannie Mae, and Freddie Mac are often discussed interchangeably, they have fundamentally different structures, mandates, and guarantee mechanisms. Understanding these distinctions is essential for evaluating the credit quality and risk profile of agency MBS.

Ginnie Mae (Government National Mortgage Association)

Ginnie Mae is a wholly-owned government corporation within the U.S. Department of Housing and Urban Development (HUD). It is the only one of the three agencies that is an actual agency of the federal government, and its MBS carry the explicit full faith and credit guarantee of the United States.

Ginnie Mae does not originate or purchase mortgages. Instead, it guarantees MBS that are backed by loans insured or guaranteed by other federal programs: the Federal Housing Administration (FHA), the Department of Veterans Affairs (VA), the U.S. Department of Agriculture (USDA), and the Office of Public and Indian Housing. These underlying loan programs serve specific populations, including first-time homebuyers, veterans, and rural borrowers.

The Ginnie Mae guarantee means that if the borrowers in a Ginnie Mae MBS pool default and the loan-level insurance (FHA, VA, etc.) is insufficient to cover losses, the U.S. Treasury stands behind the payments to MBS investors. This makes Ginnie Mae MBS functionally equivalent in credit quality to U.S. Treasury securities, though they carry additional prepayment and interest rate risk.

Outstanding Ginnie Mae MBS total approximately $2.4 trillion, representing about 25% of the agency MBS market.

Fannie Mae (Federal National Mortgage Association)

Fannie Mae is a government-sponsored enterprise (GSE), originally created by Congress in 1938 and converted to a shareholder-owned corporation in 1968. Unlike Ginnie Mae, Fannie Mae is technically a private company, though it has been under the conservatorship of the Federal Housing Finance Agency (FHFA) since September 2008.

Fannie Mae operates in the conventional conforming mortgage market. It purchases mortgages from lenders that meet its underwriting standards (known as “conforming loans”), pools them into MBS, and guarantees the timely payment of principal and interest to investors. The mortgages backing Fannie Mae MBS are not federally insured; instead, Fannie Mae's own guarantee covers losses from borrower defaults.

Fannie Mae's guarantee is an implicit government backing rather than an explicit one. There is no statutory obligation for the U.S. Treasury to support Fannie Mae's obligations. However, the federal government's actions during the 2008 financial crisis, including placing Fannie Mae into conservatorship and providing a Treasury support facility that ultimately reached $187 billion in commitments, demonstrated an unambiguous willingness to stand behind the GSE's obligations.

Outstanding Fannie Mae MBS total approximately $4.2 trillion, making it the largest single issuer in the agency MBS market.

Freddie Mac (Federal Home Loan Mortgage Corporation)

Freddie Mac is a GSE with a structure and mandate that closely mirrors Fannie Mae. Created by Congress in 1970 to provide competition and additional liquidity in the secondary mortgage market, Freddie Mac purchases conforming conventional mortgages, pools them into MBS, and guarantees timely payment to investors.

Like Fannie Mae, Freddie Mac has been under FHFA conservatorship since 2008 and carries an implicit government guarantee. Its underwriting standards, guarantee mechanism, and investor protections are functionally similar to Fannie Mae, though the two GSEs have historically differed in their specific pooling practices and mortgage purchase criteria.

Outstanding Freddie Mac MBS total approximately $3.2 trillion, making it the second-largest agency MBS issuer.

Government Guarantee vs. Government-Sponsored: Why It Matters

The distinction between Ginnie Mae's explicit government guarantee and the implicit guarantee behind Fannie Mae and Freddie Mac is more than academic. It affects pricing, regulatory treatment, and investor risk assessment.

Under bank capital regulations, Ginnie Mae MBS receive a 0% risk weight (identical to Treasuries), while Fannie Mae and Freddie Mac MBS receive a 20% risk weight. This difference in regulatory treatment means that banks holding Ginnie Mae MBS are not required to set aside any capital against potential losses, whereas Fannie Mae and Freddie Mac MBS require modest capital allocation.

In the yield market, Ginnie Mae MBS typically trade at tighter spreads to Treasuries than Fannie Mae and Freddie Mac MBS, reflecting their explicit government backing. The spread differential is usually small, in the range of 5 to 15 basis points, but it is persistent and reflects the market's pricing of the distinction between explicit and implicit guarantees.

How Agency MBS Are Created

The process of creating agency MBS follows a well-defined pipeline that connects individual mortgage borrowers to global capital markets.

It begins when a homeowner takes out a mortgage from a bank, credit union, or mortgage company. The lender originates the loan according to the underwriting guidelines of the relevant agency: Ginnie Mae standards for FHA/VA loans, or Fannie Mae and Freddie Mac standards for conforming conventional loans. These guidelines specify maximum loan amounts, minimum credit scores, debt-to-income ratios, and documentation requirements.

After origination, the lender sells the mortgage to the relevant agency (in the case of Fannie Mae and Freddie Mac) or pools it according to agency specifications (in the case of Ginnie Mae). The agency then creates an MBS by combining thousands of individual mortgages with similar characteristics, including coupon rate, maturity, and loan type, into a single pool.

The agency attaches its guarantee to the pool, promising to make timely payments of principal and interest to investors regardless of whether individual borrowers default. The MBS is then sold to investors through the TBA (To-Be-Announced) market or as a specified pool, with pricing determined by the pool's coupon rate, weighted average maturity, and other characteristics relative to current market conditions.

Once sold, the MBS generates monthly cash flows to investors. These payments consist of scheduled interest on the outstanding mortgage balances, scheduled principal repayments (amortization), and unscheduled principal repayments (prepayments) from homeowners who refinance or sell their homes.

Credit Risk Profile: Why Agency MBS Are Considered Ultra-Safe

The credit risk profile of agency MBS is fundamentally different from virtually any other yield-bearing instrument outside of U.S. Treasuries. The agency guarantee absorbs all credit losses from borrower defaults, meaning that investors face zero credit risk on their principal and interest payments.

No investor in the history of the agency MBS market has ever lost principal due to borrower default. This track record spans the 2008 financial crisis, during which agency MBS continued to pay investors on schedule even as the housing market experienced its worst downturn since the Great Depression.

The risks that agency MBS investors do bear are interest rate risk and prepayment risk. Interest rate risk is the risk that rising rates will reduce the market value of existing lower-coupon MBS. Prepayment risk is the risk that falling rates will cause homeowners to refinance, returning principal to investors earlier than expected and at a time when reinvestment rates are lower.

These risks are real and can affect returns, but they are fundamentally different from credit risk. An agency MBS investor may receive their principal back earlier or later than expected, and the market value of their holding may fluctuate, but the government guarantee ensures that all promised cash flows will ultimately be paid.

Yield Characteristics of Agency MBS

Agency MBS yields are determined by the coupon rate of the underlying mortgages, the prevailing Treasury yield curve, and the market's expectations for prepayment behavior. The spread between agency MBS yields and comparable Treasuries represents the compensation investors receive for bearing prepayment risk and for the relative illiquidity of MBS compared to on-the-run Treasury securities.

Historically, the agency MBS spread has ranged from 50 basis points in tight market conditions to over 150 basis points during periods of market stress. As of early 2026, current coupon 30-year agency MBS are yielding in the range of 5% to 6%, with spreads to the 10-year Treasury running approximately 100 to 130 basis points.

This yield profile positions agency MBS as one of the most attractive risk-adjusted income sources in fixed-income markets. They offer meaningfully higher yields than Treasuries while carrying government-backed credit quality, and they offer comparable or better yields than investment-grade corporate bonds without the credit risk associated with corporate issuers.

For retail investors and institutional allocators alike, agency MBS represent what is arguably the most efficient way to earn income on capital while maintaining a near-zero credit risk profile.

Why Agency MBS Are Ideal for Tokenization

Among all asset classes, agency MBS may be the single most compelling candidate for tokenization. Several characteristics of the asset class align perfectly with the capabilities that blockchain-based infrastructure provides.

OWNR is building the infrastructure to bring agency MBS onchain, combining the safety and yield of government-backed mortgage securities with the accessibility, transparency, and composability of blockchain-based finance. By tokenizing agency MBS from all three issuers, OWNR creates a platform where the full breadth of the agency MBS market, from Ginnie Mae to Fannie Mae to Freddie Mac, is accessible to every investor.