The S-Curve

Welcome to The S-Curve

Now you will be able to receive the latest announcements, product updates, and our insights on the mortgage market in real time.

The name of the blog, the S-Curve, is a reflection of our logo and the central feature of our prepayment model. S-curves are seen in nature in many phenomenon, from population growth to prepayment and default models. Our first S-curve, in the early 1990s, used the arctangent function, then piece-wise linear functions, and evolved over time to be more complex and vary by FICO, loan size and LTV. This evolution encapsulates both the timeless nature of fundamental relationships and constant innovation to describe them better over time.

We hope you find the information useful and we look forward to your feedback.

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Blog - Latest
  • Federal Home Loan Bank of San Francisco's Innovations in Mortgage Finance Symposium

    Richard Cooperstein

    Events

    The Federal Home Loan Bank of San Francisco directed the Urban Institute to develop innovative and actionable ideas to close the gap between white and black homeownership rates, which is as wide today as before the Fair Housing Act, enacted 60 years ago. Homeownership is crucial to a fairer society because working and middle-class families most commonly create inter-generational wealth by owning homes with amortizing mortgages. Urban Institute’s eighteen-month effort culminated in a symposium in February in Los Angeles attended by dozens of housing experts. The Borrowers Mutual Escrow Fund (BMEF), which I developed a few years ago, was included in the Urban Institute study, and I was invited to discuss it at the symposium.

    A few key themes emerged from the symposium. One centers around replacing decades-old credit scores with modern metrics that better reflect borrower financial condition as the consumer financial footprint has become increasingly digitized, especially among minority populations. These metrics generally extend beyond traditional credit profiles to include other important measures of borrower financial condition such as digitized cash flow data, telecom/utility data and others. A fair amount of evidence already shows that modernized metrics assess homeownership readiness much better than old ones. Reducing uncertainty reduces cost.

    Another theme that includes the BMEF, is that when trying to expand homeownership, liquidity and cash flow stability can be more critical to the success of marginal borrowers than traditional credit scores and down payments. Conscientious borrowers generally strive to restart paying their mortgages after short delinquencies if given the chance. Empirical support for this view includes delinquency performance through repeated climate events (e.g., hurricanes and floods) and the success of generalized forbearance during the COVID-19 pandemic.

    This has turned decades of loss mitigation wisdom on its head. The Massachusetts state mortgage insurance program has included unemployment benefits for almost 20 years to resounding success. This program provides borrowers with fragile liquidity and volatile income, with a few months of payment reserves between jobs (e.g., consistently succeeds in preventing delinquency even through the financial crisis of 2007 and the COVID-19 pandemic). The GSEs and FHA have now made forbearance their initial loss mitigation response to borrower delinquency.

    The BMEF proposes that borrowers put 3% of their house value into an administered escrow account instead of towards a down payment. It’s well-known that reserves are crucial to borrower success and placing reserves into escrow to be used for income interruption or unexpected maintenance will make reserves even more effective. Money in such accounts will always reduce risk compared with small down payments for borrowers, servicers, mortgage insurers and guarantors. This is provably true because the escrow funds are very liquid for payments, while the liquidity value of small down payments is effectively zero. Further evidence is that reperformance rates for delinquent borrowers are higher for borrowers with lower credit scores than for those with higher credit scores.

    Borrowers pay mortgage insurance and guarantee fees to compensate insurers for risk, but it does not impact borrower ability to pay. By contrast, putting aside borrower funds for financial stress reduces risk throughout the value chain. Since it is borrower money in the first place, no subsidy is needed, but risk declines because liquidity is improved. Finally, borrower escrows managed by servicers for taxes and insurance are individual. However, BMEF escrows can be combined across borrowers to generate large diversification gains. Even among traditionally risky borrowers, perhaps 75% of them will never become delinquent, so it’s likely that the benefit limit can exceed the average contribution.

Blog - Archives

The S-Curve Archives

  • Vivian Li, Rob Landauer

    Events

    Andrew Davidson & Co., Inc (AD&Co) proudly sponsored IMN’s 11th Annual Mortgage Servicing Rights (MSR) Forum by Informa at the New York Hilton Midtown. Senior modeler Daniel Swanson joined the “Managing Delinquencies & Forbearance Value” panel in discussing how servicers are adapting to today’s market and the evolving delinquency trends.

  • Kevin Lin, Eknath Belbase

    Podcast

    Tune in to our fourth episode of AD&Conversations with Kevin Lin and Eknath Belbase, our product lead for our Climate model. In this episode, they discuss the new Climate Impact Suite (CIS) pilot project, and Belbase outlines several challenges the team is navigating, including:

  • Kevin Lin, Eknath Belbase

    Podcast

    Tune in to our fourth episode of AD&Conversations with Kevin Lin and Eknath Belbase, our product lead for our Climate model. In this episode, they discuss the new Climate Impact Suite (CIS) pilot project, and Belbase outlines several challenges the team is navigating, including:

  • Andrew Davidson

    Podcast

    Andrew Davidson was invited to speak on Equifax's Market Pulse Podcast titled, "Driving Efficiency and Resilience in the Mortgage Industry" live at the 2025 MBA Annual Convention in Las Vegas. 

    Andy explains how variations in data files can distort risk assessment, creating a dual risk for lenders: extending credit to borrowers more likely to default while overcharging customers whose risk is overstated. 

  • Richard Cooperstein

    Thoughts

    Our latest Policy Perspective written by Richard Cooperstein offers an analysis of the U.S. housing and mortgage finance markets, focusing on key trends and forward-looking risks. While housing markets are not fully efficient, they do respond to economic imbalances which create opportunities and vulnerabilities. This article explores how demographic shifts, credit access, interest rates, and climate risks shape both housing demand and supply.

    Key findings include:

  • Kevin Lin, Richard Cooperstein

    Podcast

    Join Kevin Lin in a conversation with Richard Cooperstein as they dive into Kinetics, AD&Co's modular platform designed to deliver the full power of our models and analytics; with the flexibility to license only the tools you need.

  • Andrew Davidson

    Thoughts

    The latest Policy Perspectives paper “Competing Claims in Privatization of Fannie Mae and Freddie Mac” is now available!

    Nearly 20 years ago, on September 6, 2008, the GSEs, Fannie Mae and Freddie Mac entered conservatorship. Since that time there have been many proposals to restructure, eliminate or release the GSEs. Once again there is talk about the privatization of Fannie Mae and Freddie Mac.

  • Tom Parrent

    Thoughts

    AD&Co held our annual employee meeting in Detroit, Michigan. In addition to gathering everyone in person to socialize and strategize, we use these annual meetings to learn about different cities, especially with regard to housing market dynamics.

    We chose Detroit because the oft-maligned city is undergoing a significant renaissance, and we wanted to explore the area and learn how housing may have played a role in both Detroit’s decline and rebirth.

  • Niraj Tailor, Hikmet Senay

    Products

    Andrew Davidson & Co., Inc (AD&Co) is pleased to announce the beta release of MARS+, the next generation of Mortgage Analysis & Reporting System (MARS), which has been in use since 2008 for performance reporting of AD&Co models. MARS+ aims to provide enhanced and advanced capabilities and features for mortgage analysis and reporting.

    The new enhancements of MARS+ include:

  • Eknath Belbase, Laura Silberg, Aidan Loftus, Joni Baker, Sam Sutton, Richard Cooperstein

    Events

    Several AD&Co employees attended SFVegas 2025. This post shares their unique perspectives from attending the conference and key takeaways from the sessions.