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.

Subscribe to our publications to make sure you stay up to date
Blog - Latest
  • Gritty Renaissance: AD&Co Visits Detroit

    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.

    From the early 1900s through the mid-1960s, Detroit was an industrial and innovation powerhouse. Beyond automobiles, the southeastern Michigan area attracted new residents with jobs in everything from heavy industry to machine shops to transportation.

    Detroit has always had a substantial share of single-family houses compared to other industrial hubs, which relied more on high-density multifamily housing. While homeownership rates were generally high, opportunities were not evenly dispersed, as racial redlining led to largely segregated neighborhoods and lower homeownership rates among blacks and ethnic minorities. Although redlining was common in the first half of the 20th century in many large American cities, Michigan set itself apart.  Its Home Rule Act allowed a great deal of self-governance by small cities leading to the creation of dozens of very small towns, all with different public services and both subtle and overt discriminatory policies. The Home Rule Act also allowed large companies to heavily influence local taxation policy and effectively create low tax havens in small towns, thus starving the greater Detroit area of tax revenue.

    Detroit started facing significant troubles in the late 1960s, as the 1967 race riots led to significant white flight. The OPEC embargo in the early 1970’s increased oil prices and opened the door to more fuel-efficient foreign competitors in auto manufacturing. The city’s decline began with significant population loss due to both unemployment and migration to suburban areas, resulting in deterioration of inner-city housing stock and severe underfunding of public services such as police, fire protection and education.

    Long known for its grit and determination, Detroit started to come back in the 1990s and early 2000s as the auto industry recovered. However, much of that progress was lost during the Great Recession due to predatory lending and the second collapse of American automakers. Many large blocks of the inner city were left with only one or two houses standing, and arson for insurance money plagued the housing stock.

    However, Detroit’s revival in the past ten years proved even bigger than all of its setbacks. The Lions, Tigers, Red Wings, and Pistons now all have their venues within easy walking distance of the revitalized downtown business and entertainment district. The city built a new riverfront parkway and renovated parks. Downtown has incredible energy once again, with bustling businesses and residential towers going up, not to mention the burgeoning art scene popping up in multiple locations.

    Laura Grannemann, Executive Director, Rocket Community Fund & Gilbert Family Foundation, gave an overview of the organizations' endeavors in the community. As one of the nation’s largest mortgage lenders, their Detroit Home Repair Fund and Detroit Tax Relief Fund work to head off displacement through preventing tax foreclosure and eviction.

    Detroit still faces many challenges, particularly in those neighborhoods hit hardest by out-migration, foreclosures, and underinvestment in city services. Wealth and influence remain highly concentrated, and the Home Rule Act micro towns remain an impediment to healthy Detroit finances and provision of basic services. Despite this, we found encouraging pockets of home-grown revitalization. Jeanette Pierce, president of City Institute, showed us how hyper-local organizing is bringing growth and renewal without troublesome gentrification and displacement. We met leaders from organizations such as the Southwest Detroit Business Association, Capital Impact Partners, and Live6 Alliance that advocate for fair housing and community engagement. Keeping people in the neighborhoods that multiple generations have called home is a hallmark of these local initiatives. Tactical rezoning has helped overcome some of the obstacles to development presented by Detroit’s traditional focus on detached single-family housing.

    The team also met Ike Blessitt, who personifies Detroit’s gritty reputation. Ike grew up in Hamtramck, one of the Home Rule Act towns completely surrounded by Detroit. As a four-sport high school star athlete, Ike attracted the attention of Detroit Tigers scouts and eventually made it to the major leagues with the 1972 Tigers. Today, even as a 76-year-old double amputee, Ike has continued his 15 years of teaching individuals, aged 6 to 60, how to play baseball. Like the development efforts, Ike keeps it local to help inner-city kids by building a complete baseball training facility in his Detroit backyard. The Ike Blessitt Sports Academy attracts kids from throughout Detroit.

    We came away from Detroit with a real appreciation for the daily challenges its residents overcome through innovation and community organizing. The lively sports and entertainment district will surprise new visitors, but digging deeper into the neighborhoods will show that this renaissance is just getting started.

Blog - Archives

The S-Curve Archives

  • Mickey Storms, Alex Levin

    Thoughts

    Recently, 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.

  • Rob Landauer, Abe Martin

    Podcast

    Join 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

  • Ashlea Bonds

    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.

  • Sanjeeban Chatterjee, Vivian Li, Joni Baker, Richard Cooperstein

    Thoughts

    Building 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.

  • Joann Gollette

    Events

    Andrew 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.”

  • Eknath Belbase, Daniel Swanson, Yvonne Chen

    Events

    AD&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.

  • Alex Levin

    News

    AD&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.

  • Joni Baker, Sanjeeban Chatterjee, Richard Cooperstein, Andrew Davidson

    Thoughts

    In 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.

  • Joann Gollette

    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.

  • Sanjeeban Chatterjee

    Thoughts

    There 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.