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
  • Mortgage Origination in a Post-COVID-19 World

    Vivian Li

    Thoughts

    In this blog post, we used the recently updated Mortgage Market Statistical Annual to examine the dynamics of residential loan origination by state and by market segments and highlight important trends.

    From mid-2020 until April 2022, the Fed Funds rate was zero and fixed rate mortgage rates were historically low at about 3% (see Figure 1). Thereafter, the Fed began raising the Fed Funds rate to 5% today and fixed rate mortgage rates have doubled. Mortgage payments became unaffordable to many potential buyers and the mortgage origination volume dropped drastically across market segments and states by 80%. Predictably, the refinance market disappeared. Figure 2 shows that the origination volume for different mortgage products decreased drastically from Q1 2021 to 2023.

    Figure 1. 30-Year Mortgage Rate, Fed Funds Effective Rate and PCE Price Index

    Figure 1. 30-Year Mortgage Rate, Fed Funds Effective Rate and PCE Price Index

     

    Figure 2. Origination Volume by Market Composition (Dollars in Billions)

    Figure 2. Origination Volume by Market Composition (Dollars in Billions)

    Homeowners with low-rate mortgages have a strong financial incentive not to sell when facing the prospect of buying a new house with a mortgage rate twice as high (lock-in effect). These homeowners on the sidelines reduce both the supply and demand for housing. The countervailing impacts on price make the ultimate effect unclear; prices could rise or fall, but the changes are likely to moderate.

    Figure 3 shows two things; (1) the housing price spike during the pandemic when rates were so low and the predicted recent collapse when rates rose and (2) turning points in housing prices lead to turning points in new construction rates weighted by population.

    Figure 3. Housing Units Under Construction vs HPI

    Figure 3. Housing Units Under Construction vs HPI

     

    Looking at the States

    Across the 50 states, plus Washington D.C. and Puerto Rico, origination dropped 48% from 2021 to 2022. For some background, YoY changes for the past few months have been positive, with 2019 to 2020 year-over-year (YoY) showing a 78% increase. We have to go back to 2016 to 2017 to see a negative 10% YoY drop and 2017 to 2018 a negative 9% drop. Among the most populous states, California suffered the largest drop YoY, declining by a whopping 60%. Some other states with a big YoY drop in origination include Maryland, 55%, Virginia, 54% and Massachusetts, 53%. On the other end, Texas and Florida had the smallest YoY losses at around 33%.

    Figure 4 Originations by State

    Figure 4 Originations by State

    The situation in California, the most expensive state with the most expensive housing market was obvious; the escalating rate hikes priced many potential buyers out of the housing market in a state already hurt by the high income and property taxes.

    The situations in Florida and Texas were drastically different. As low tax states, they represented good buying options even in a severe market turn and suffered the least drops.

    Naturally, people are motivated to move to more tax-friendly states such as Florida when they retire. As the global pandemic hit and changed how people live and work, it further amplified that migration trend. Workers who once needed to live in states with hot employment markets like California’s tech hub can now work remotely and leave for other lower-cost states.

     

    From Refinance to Purchase

    The ten consecutive Fed rate hikes eliminated the refinance boom and deterred existing borrowers from moving, a combination leading to the plunge of origination. The refinance share has fallen from 71% in Q1 2021 to 16% in Q4 2022. On the turnover side, purchasing activities are still ongoing amidst the high rate environment. Purchase volume is not as drastically changed but still has fallen 13% from 2021. Figure 3 still shows a very steady volume of purchase originations over the past two years, despite its obvious decline over the past months. The decrease of the purchase volume can be attributed to the “lock in effect.”[1] The lock in effect is visible for discount mortgages as it deters potential sellers from giving up their current low-rate loan and finance next property with a more expensive one even if they have plans to relocate.

    Figure 5. Purchase vs Refi Origination Volume (Dollars in Billions)

    Figure 5. Purchase vs Refi Origination Volume (Dollars in Billions)

     

    Looking Forward

    We will continue to monitor changes in origination trends and their connection with affordability and home prices in our borrower behavior and home price modeling. For additional insight, read AD&Co’s HPI Outlook Update by Alex Levin.[2]

     

    [1] Baker, Joni, and Daniel Swanson. “How to Use AD&Co’s Deep Discount and Super Premium S-Curve Tuning.” Quantitative Perspectives (May 2023).
    [2] Levin, Alex. “AD&Co’S HPI Outlook Update: Flat, But Multidirectional.” The Pipeline, no. 182 (June 2023).
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.