Standard & Poor’s issued a research report, What Drives the Variation Between Conforming and Jumbo Mortgage Rates? It opens,
What drives the variation between the conforming and jumbo mortgage rates for the 30-year fixed-rate mortgage (FRM) product offered in the U.S. residential housing market? While credit and interest rate risk are the main factors at play, S&P Global Ratings explores how these risks relate to capital market execution and whether this relationship translates into additional liquidity risk. In our study, we compare the historical spreads between the two average note rates over time, and we also examine the impact of certain loan credit characteristics. Our data indicate that the rate difference grows in periods for which the opportunity for securitization declines as a viable exit strategy for lenders. (1)
S&P also finds that “[r]isk-based pricing trends also appear to influence the jumbo-conforming spread” and that “[t]he currently narrow spread suggests that a combination of g-fee increases and jumbo credit migration has, to some extent, counteracted the lack of liquidity in the non-agency market.” (1)
The report offers some concise background:
The 30-year FRM is a product unique to the U.S. residential housing market. Lenders in other countries typically offer adjustable-rate or balloon mortgages, which serve as the primary debt tools for housing finance. The 30-year FRM has not been globally adopted, partially because the long-term amortization schedule can saddle a lender with substantial interest rate risk in addition to potentially prolonged credit risk. However, the structure of the mortgage financing system in the U.S. provides an exit strategy: lenders can typically sell loan pools into a reasonably deep market if they are averse to the credit, duration, or convexity risks posed by these long-term assets.
In the U.S., the majority of mortgage financing is channeled through government-sponsored enterprises (GSEs) Fannie Mae and Freddie Mac, which have a mandate to buy mortgages for their own portfolios and securitize loan pools, which are subsequently sold to investors. Mortgages that are not financed via the GSEs are often either securitized in the non-agency market or held in institutional portfolios. Both agency and non-agency securitizations optimize funding sources and liquidity, thereby allowing homeowners to enjoy relatively low mortgage rates across the U.S. (1)
My main takeaways from the report are that (1) the decrease in securitization since the financial crisis has contributed to a wider spread between jumbo and conforming mortgages; (2) the high guaranty fee for conforming mortgages pushes down the spread between jumbo and conforming mortgages; and (3) the credit box appears to be loosening a bit, which should mean that jumbos will become available to more than the “super-prime” slice of the market.