Session 4A is Now Live!
We just published our one-step compliant baseline model—built on real-world resort town residential data. 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
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