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.
-
Ability-To-Repay Benchmark UpdateThoughts
Summary
In 2021, Andrew Davidson & Co. Inc. (AD&Co) proposed a benchmark cohort approach to setting Ability-to-Repay (ATR) Qualified Mortgages (QM) standards. Successful benchmarks based on data are model-free and transparent, and the cohorts must perform consistently in comparison to one another and across time. Our original work used data through the early stages of the pandemic when non-performing loan percentages skyrocketed. This update shows that the cohorts continue to perform consistently.
To review; the metric is 60+ DQ (delinquency) rates at 24 months old for loans guaranteed by GSEs, FHA, VA, and non-QM securitizations. We update performance through late 2021 or early 2022 depending on the data source. The update turned out to be six to nine months past the peak non- performance rates (60+ DQ + Forbearance) of the pandemic. One of the best tests of reliability are cohorts that perform consistently at significant turning points. We show two different examples of cohort performance which all pass with flying colors.
Figure 1 extends the original time-series delinquency graph by cohort across combined federal segments (GSE, FHA, VA) and shows consistent performance through the two sharp turning points in delinquencies from the lows before the pandemic and the peak thereafter.
Figure 1. Delinquency Rates by Cohort

Figure 2 extends the time-series graph that compares the ‘FHA Average’ cohort for each of the three federal segments, GSE, VA, FHA, and non-QM. The ‘FHA Average’ cohort is roughly 95 LTV, 680 FICO, 40 DTI for government lending, and about 90 LTV, 680 FICO for non-QM. The results continue to illustrate that the benchmark cohorts perform consistently across market segments.
Figure 2. Delinquency Rates for ‘FHA Average’

Conclusion
The pandemic and the federal response to it are unprecedented in modern times for their impact on the US economy and housing market. Nevertheless, mortgage cohorts performed consistently over the last several years across federal and non-QM segments, increasing confidence in this approach. This stability contrasts with the vastly higher non-performance rates of the subprime and reduced documentation era that resulted from poor lending practices, as we reported in the original study.
This highlights that conscientiously measuring income is essential to consistency.
The S-Curve Archives
-
Thoughts
The growing prevalence of artificial intelligence in the mortgage industry is shining a new light on the human biases that have pervaded the industry since its inception. AI is meant to bring fairness and objectivity to mortgage decisions, but it can’t perform fairly if it was built on an unfair system.
-
Products
The LDM v3.0.2 library adds AutoLDM to the v3.0.1 library.
Key benefits include:
-
EventsWe at Andrew Davidson & Co., Inc. (AD&Co) are once again thrilled to celebrate Pride Month, especially the contributions of LGBTQ professionals in the field of finance including affordable housing policy and the GSEs. This year, in addition to celebrating, we are also paying increased attention to the challenges that LGBTQ individuals face, particularly around issues of housing. Our pride in our LGBTQ staff and community sits alongside our concern about discriminatory lending practices, including in mortgages. As of February 2021, for the first time, lesbian, gay, bisexual, transgender, queer, and questioning (LGBTQ) Americans will be protected from housing discrimination under the Fair Housing Act.
-
News
For several years, AD&Co has tracked the total rate of return (TRR) performance of the GSE CAS and STACR CRT in its U.S. Mortgage High-Yield Indices. The AD&Co Mid-Tier index constitutes a broad market measure of the TRR performance of GSE CRT. The related sub-indices segregate the CRT market into 4 index Tiers by attachment point, reflective of the credit exposure of the various classes of underlying CRT ranging from B to M1.
-
EventsWe at Andrew Davidson & Co., Inc. (AD&Co) stand in solidarity with the Asian community and speak out against the xenophobic ignorance that has led to increased racist attacks against Asians. We protest against these hate crimes. This is a time to celebrate the richness that we have gained from the diversity of the Asian culture. We pledge to support the heritage that is part of what makes us American.
-
Events
What does it mean to be mentally healthy? The answer is different for everyone. With all the extra anxiety that many of us have experienced since 2020, whether from uncertainty about COVID-19 or from other experiences that may be new to us, it’s important to acknowledge that it’s alright to not feel alright. Fortunately, there are numerous resources that are available locally, nationally, and in some cases through your workplace or benefits package. We might start by finding out what makes us feel better.
-
Products
Today marks the publication of Chris Widman's Quantitative Perspective, a comprehensive article on the newest member of our LoanDynamics suite, the Auto LoanDynamics Model. Auto LDM will be integrated into vendor systems and AD&Co tools, allowing users to perform analysis on auto loan and ABS positions.
-
EventsSince 1970, April 22nd has been the annual day to appreciate our planet and recognize the importance of protecting it. But more and more, we realize that everyday needs to be Earth Day, and that we need to take better care of the place that gives us life.
-
Thoughts
To seek "causes" of poverty in this way is to enter an intellectual dead end because poverty has no causes. Only prosperity has causes. – Jane Jacobs, Activist and Author
-
Events
CRTcast, a new podcast series under Freddie Mac’s Home Starts Here programming, focuses on credit risk transfer (CRT) and it’s three spokes: securities, (re)insurance and mortgage insurance. Freddie Mac leadership together with CRT industry experts cover current and relevant topics.