The Final Call: Is Legacy CAMA Surviving the Audit?

For decades, the entrenched legacy mass appraisal system has been the undisputed Champ of property tax administration—heavy, rigid, and legally anchored. But a single-entry Champ cannot survive a double-entry world.

Today, we are dropping the final teaser for Session 4B, and the numbers leave the old guard with nowhere to hide. When you run raw, population-level data through a single regression model without a dual-pass accounting audit, the Single-Entry Mass Appraisal splits your jurisdiction right down the middle:

·  In-Town: Property values are systematically overestimated relative to our model. Homeowners inside the town are being over-assessed and over-taxed.

·  The Suburbs: Property values are systematically underestimated, granting an artificial valuation discount and leaking massive institutional revenue.

There is a new kid in town. The Challenger—the DEMA™ Protocol—has officially stepped into the ring.

Double-Entry Mass Appraisal (DEMA™) doesn’t illegally alter the official record. Instead, it acts as an agile, independent forensic audit that exposes exactly where the Champ's blind spots are, turning neighbors against each other and setting the stage for an econometric equalization of the tax roll.

The talk on the street is changing, and the old single-entry playbook is officially on notice. This is your last chance to unpack the structural distortions of Session 4B before we move to the final reconciliation.

Read the final Session 4B analysis and watch the Challenger land the ultimate econometric punch:

Link to the Substack Post

Link to the Patreon Post

If you work in assessing, serve on a VAB or Review Commission, or consult in this space, DEMA™ offers a practical path to stronger rolls and fewer appeals.

Tag colleagues who should see this series:

#DEMA #CAMA #DataScience #Econometrics #IAAO #MassAppraisal #RegressionModel #PropertyTax #ValuationModeling #HorizontalEquity #TaxLitigation

Introducing DEMA™ (Double-Entry Mass Appraisal)

What if the traditional one-step CAMA approach is the root cause of the appeals tsunami?

We’ve been building a better way.

In Sessions 4A and 4B, we demonstrated the complete Double-Entry Mass Appraisal (DEMA™) protocol:

· First Entry (Sales-Based Modeling): Builds the tentative roll with econometric soundness (BLUE status) and IAAO compliance.

· Second Entry (Population-Based Equalization): Cleans the roll by identifying and correcting population-level distortions before it is finalized.

This two-sided ledger approach — DEMA™ — is the true Nirvana of modern mass appraisal: proactive equity instead of reactive defense.

Session 4C, the grand finale of Phase 1, will deliver the final Champ-Challenger showdown between the Central Taxing District and the Town Taxing District. This direct comparison will identify the major faultlines when the jurisdiction roll is generated by two separate models (in-town vs. suburbs). 4C will complete our end-to-end DEMA™ solution next week.

To read Session 4B and run the DEMA™ Protocol on your own database:

Link to Substack

Link to Patreon

If you work in assessing, serve on a VAB or Review Commission, or consult in this space, DEMA™ offers a practical path to stronger rolls and fewer appeals.

Tag colleagues who should see this series:

#DEMA #CAMA #IAAO #MassAppraisal #PropertyAssessment #ValuationModeling #VAB 

Why Mass Appraisal Needs Double-Entry Valuation Modeling

Would you let a Fortune 500 company manage its financial ledger using single-entry bookkeeping?

Of course not. Tracking cash flowing in without a balancing entry, a trial balance, or a structural balance sheet is an immediate recipe for systemic failure.

Yet, every single year, multi-billion-dollar tax jurisdictions run their property rolls on the exact same single-entry mindset.

Legacy CAMA practices do this by default:

1.   They look at transaction data (sales).

2.   They run a baseline regression.

3.   They print the Tentative Roll (the first entry).

4.   They stop right there.

Stopping at the first entry means you are flying completely blind. You have no balancing ledger to check if those values are mathematically stable or legally uniform across the remaining 95% of the unsold population. You only find out the ledger is broken when an appeals tsunami hits the Value Adjustment Board (VAB) or the Review Commission.

In Session 4B, we introduce modern Double-Entry Valuation Modeling. We show you how to take that initial generative sales engine and systematically reconcile it against a full population dataset of 60,870 properties.

If you want to move past single-entry mass appraisal and learn how to build an unassailable, balanced valuation ledger that stops litigation before it starts, the Session 4B blueprint is officially live.

The Executive Summary remains free for everyone (use either link below):

Link to Patreon

Link to Substack

How Resilient is Your Tax Roll when subjected to a Rigorous Population-Based Audit?

 Session 4B is Now Live!

Many mass appraisal systems look brilliant on paper. They boast high R^2 values, strong global F-statistics, and highly "significant" variables. But beneath the surface of these global metrics often lie structural anomalies, negative coefficient traps, and systemic equity distortions that leave jurisdictions incredibly vulnerable to appeals and litigation.

In Session 4B of our Equalization Valuation Modeling series, we move from sales-based modeling (Session 4A) to a comprehensive population dataset of 60,870 Single-Family Residences.

Using a population-based approach, this session provides a step-by-step blueprint for assessment staff, independent consultants, Review Commissioners, and Value Adjustment Board (VAB) members to conduct a forensic audit of a tentative roll, diagnose legacy computer-assisted mass appraisal (CAMA) failures, and protect the integrity of the jurisdiction.

In this session, we dive deep into:

The Continuous Variable Riddle: Why legacy linear models produce economic absurdities (like negative land values) and how to fix them using our proprietary, objective, stratification method. 

Quantifying Systemic Exposure: How a seemingly simple binary variable can unmask massive, multi-billion dollar horizontal and vertical equity risks across a population. 

The 2-Pass JVR Protocol: How executing a strict two-pass regression with Just Value Ratio (JVR) analysis mathematically purges cross-jurisdictional noise and stabilizes the roll.

This session also sets the stage for our upcoming grand finale: The Session 4C Champ-Challenger Showdown.

If you are an assessor, independent analyst, or oversight commissioner looking for unassailable, platform-agnostic modeling frameworks to navigate today's complex valuation landscape, this playbook is for you.

Read the Executive Summary for Free and unlock the full Premium Deep Dive here:

Substack Link

Patreon Link

Equalization Valuation Modeling (EVM) for Smaller and Mid-Sized Jurisdictions: Foundations & Model Development

 

Equalization Valuation Modeling (EVM) for Smaller and Mid-Sized Jurisdictions: Foundations & Model Development: (Building Practical, Transparent Models Using Your Own Just Values)

In this book, we introduce Equalization Valuation Modeling (EVM) — a practical, transparent approach designed specifically for smaller and mid-sized jurisdictions. Unlike traditional Automated Valuation Models (AVM) or Mass Appraisal Models (CAMA) that predict sale prices, Equalization Valuation Models use your jurisdiction’s own Just Values as the dependent variable to improve uniformity and defensibility across the roll.
Using a real non-coastal county dataset (hybrid taxing system with 7 towns), we demonstrate:

• Proper data construction for equalization modeling
• The 2-Pass Outlier Protocol (Z-score based)
• Dramatic model improvement from Pass 1 to Pass 2
• Just Value Ratio (JVR) analysis showing major gains in uniformity

Key Result: After removing ~5% outliers, R² rose to 93.78%, Standard Error dropped to $35,963, and JVR dispersion tightened significantly. This book lays the forensic foundation for building lightweight, internally manageable models using only Excel.

This concise book establishes the core of Equalization Valuation Modeling — a transparent, platform-agnostic approach that serves as both a preventative shield for assessing offices and an independent verification standard for Review Commissions, Value Adjustment Boards, and consultants.

Only $2.99 -- Kindle version (for a limited time).

Link to the book's Amazon Kindle version

The Classic One-Step Sales Sample-Based CAMA Approach and the Three Golden Guardrails™ are live on Patreon and Substack.

 Session 4A is Now Live!

We just published our one-step compliant baseline model—built on real-world residential data from a Southern resort town (Spoiler Alert: Not Orlando, Miami, or Tampa). The quality control ledger is undeniable:

· COD = 8.54%

· PRD = 1.010

· R^2 = 0.8441

· SE = $55,333

· Status: Stage 1 BLUE. IAAO 3.3.5 Compliant.

On paper, it’s an assessor’s dream. In the field, it’s still blind to 95,000 taxpayers.

This is the exact structural trap that triggers the modern property tax appeals tsunami. Traditional workflows hit an elite, compliant ratio on a small sales sample and call it a day, completely masking the localized boundary rot that slaughters your roll in court. Achieving Stage 1 BLUE status does not guarantee Stage 2 population equity.

Inside the Paid Subscriber Session 4A Manual:

· The 2-Pass Protocol: The exact forensic roadmap to transition from raw, chaotic sales data to a certified, unassailable baseline model.

· The Three Golden Guardrails™: Hard-coding non-negotiable rules for Percentile-Based Sampling, strict Holdout Testing, and an absolute ban on on-the-fly GIS variables.

· The Shock Sample: A targeted, 24-sale micro-audit proving how a mathematically “perfect” model can still catastrophically fail your broader jurisdiction.

· The Doctrine: A masterclass on why global IAAO compliance is a necessary operational milestone, but an entirely insufficient condition for absolute tax equity.

· Predicting Distortions: How to use front-end sample variance to accurately forecast exactly where your Tentative Roll will rupture before it goes public.

One-step is clean. Two-step is constitutional.

Session 4A is the model. Session 4B is the roll. This ends the era of “good enough” COD.

NOT A PAID SUBSCRIBER YET?

The complete Phase 1 Executive Summary is 100% FREE for everyone. Read the structural breakdown of the guardrails and the limits of sample-based calibration before you touch a line of code.

Access Session 4A here:

https://www.patreon.com/SidSom/posts/session-4a-one-163206609

https://sidsom.substack.com/p/session-4a-the-classic-one-step-sales

Please tag colleagues who should see this series.

#CAMA #IAAO #MassAppraisal #PropertyTax #ForensicValuation #ValuationModeling #DataScience #Econometrics