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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Federal Home Loan Bank of San Francisco's Innovations in Mortgage Finance SymposiumEventsThe 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.
The S-Curve Archives
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ThoughtsRecently, aggregators have crossed market borders by issuing residential mortgage-backed securities (RMBS) backed by owner-occupied (OO), GSE-eligible conforming loans. Additionally, conforming mortgage loans have drawn investment interest from insurance companies fronted by aggregators and evaluated by third-party firms. These developments constitute historically rare disintermediations of the nearly monopsonist purchases of conforming loans by the GSEs.
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PodcastJoin Rob Landauer in a conversation with Abe Martin as they discuss his recent Pipeline article, "Modeling the Balance Behavior of HELOC Borrowers." In this episode, they highlight key points from the article as he shares insights into the draw component of HELOCs and provide an update on the beta rele
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News
We’re excited to announce a major addition to the Andrew Davidson & Co., Inc. (AD&Co) team. Industry leaders Kelli Sayres and Gene Park, known for building and scaling leading fixed-income analytics platforms, have joined AD&Co’s Business Development team.
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ThoughtsBuilding on our earlier research on expanded consumer attributes, AD&Co continues to explore how credit data contributes to modeling delinquency and prepayment risk, which are key drivers of mortgage servicing rights cash flows and valuation.
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EventsAndrew Davidson recently joined NFM Lending’s Greg Sher on the One On One podcast to discuss our recent white paper, “The Impact of Moving Away From the Tri-Merge Standard.”
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EventsAD&Co recently sponsored and attended SFVegas 2026 and Optimal Blue Summit 2026. This post shares the AD&Co team's unique perspectives and key takeaways from attending both conferences.
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NewsAD&Co US Mortgage High Yield Indices
The Federal Reserve Economic Data (FRED) portal, housed by the Federal Reserve Bank of St. Louis, has been publishing AD&Co’s CRT indices since 2019. These series posted under the overall name of “US Mortgage High-Yield” include total return rates and credit and option-adjusted spreads (crOAS) – a projected return’s spread over Treasury (in the past, Libor). These series are available going back to 2014-end and tiered by CRT initial supports.
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ThoughtsIn July 2025, the US Federal Housing Finance Agency (FHFA) announced that the government-sponsored entities (the Enterprises or GSEs), Fannie Mae and Freddie Mac, would permit lenders to choose between Classic FICO and VantageScore 4.0 credit score models for loans sold to the GSEs. FHFA also stated in a social media post that the tri-merge standard would be maintained for mortgage underwriting. Nevertheless, some mortgage industry stakeholders recommend moving away from the tri-merge standard for GSE mortgages in favor of a single or bi-merge report standard.
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News
As housing faces more climate threats that result in more losses, the insurance program that it sits on is teetering on the brink of collapse. Yet, the home insurance market has three distinct stakeholders that have competing priorities, and today, there is no motivation for a collaborative solution.
Understanding how to strengthen and protect the current structure requires looking at the cost burdens along with the risk for each of those parties.
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ThoughtsThere has been a flurry of activity in the mortgage markets since the 2018 passage of the Economic Growth, Regulatory Relief, and Consumer Protection Act. This act requires the Federal Housing Finance Agency (FHFA, now known as US Federal Housing) to validate and modernize the credit score models used in the housing finance system. It should be noted that so far, the discourse has been around mortgages sold to the Enterprises (Fannie Mae and Freddie Mac). Ginnie Mae has not provided any guidance on their plans to start using new credit score models.