Luc Hermans - Ratio Studies, GWR and the Netherlands

The best assessors I know share a common trait: they're always looking beyond their own jurisdiction's borders. Not to copy wholesale, but to understand the fundamental challenges we all face, and the creative solutions emerging worldwide.

I was reminded of this recently listening to Luc Hermans from the Netherlands Council for Real Estate Assessment. While their property tax burden is a fraction of ours (hundreds versus thousands annually), their pursuit of fairness and uniformity mirrors our own struggles exactly.

The Universal Challenge: Market Volatility Meets Annual Cycles

Hermans articulated something every assessor knows in their bones: "Over the last couple months, really, maybe the last two years, the market has been quite crazy. We saw huge increases in prices... And then basically, since a couple of months ago, we're seeing this decline."

Sound familiar? Whether you're in Amsterdam or Atlanta, capturing accurate values during market turbulence while maintaining year-to-year consistency is perhaps our profession's greatest test. The Dutch face this with annual revaluations, a practice that keeps values current but demands exceptional operational efficiency.

The tight timeline creates its own pressures. As Hermans noted, "If you don't have it in check at the beginning of the year, it's very hard to... get in front of the eight ball again." Those of us on annual cycles know this dance well. There's no room for data quality issues or process inefficiencies when the calendar is your taskmaster.

Beyond Traditional Metrics: The Evolution of Equity Measurement

What caught my attention most was Hermans' excitement about applying the Gini coefficient to assessment quality measurement. Traditionally used in economics to measure income inequality, this metric offers a fresh lens on assessment equity.

"It's more of a development from development economics, but it's now being applied in property tax," he explained. This represents a shift from simply measuring accuracy to understanding the distribution of assessment quality across different property types and value ranges.

For those of us who've spent careers focused on CODs and PRDs, this might seem like unnecessary complexity. But consider this: our traditional ratio studies tell us if we're accurate and consistent, but do they fully capture whether our systems treat all property owners equitably? The Gini coefficient approach examines "value share rather than the ratios on their own," potentially revealing patterns our current metrics miss.

The Technology Horizon: From GWR to 3D Modeling

Hermans' background in geography brings valuable perspective on spatial modeling techniques. His enthusiasm for geographically weighted regression (GWR) reflects a growing recognition that property values aren't just about characteristics, they're about location-specific relationships.

"It's essentially a multiple linear regression, but on every point you have in your study area," he explained. While computationally intensive, GWR offers the explainability of traditional models with the nuance of modern machine learning approaches. It's the kind of tool that bridges the gap between "black box" AI and the transparency our profession demands.

Looking ahead, Hermans sees potential in building information models and 3D city analysis: "If we can do vision lines or even the sun exposure of a balcony... that would be awesome to play around with." These aren't just technical toys, they represent our ability to capture and quantify the subtle factors that drive real market value.

The Human Element: Building Expertise Through Mentorship

Despite all the technical innovation, Hermans' advice for newcomers was refreshingly human: "Find a mentor... it's going to make or break your experience." He credited much of his rapid development to being "in touch with the right people. Eager people are eager to teach."

This resonates deeply. Our field combines technical complexity with public accountability in ways few professions match. Having someone who can help navigate both the mathematical models and the political realities is invaluable. As Hermans noted about his own journey: "I really learned on the job on the go, which was a great experience for me."

His practical advice for skill building was equally grounded: "Find a data set on the Internet... just go play around with RStudio or Python or whatever floats your boat... you'll pick it up in the end and it's going to be a struggle. But you'll get there."

Learning From Each Other

The Dutch system offers interesting contrasts to our own. Their oversight structure, with the Council conducting audits and providing technical guidance, creates a different dynamic than our state-level oversight. Their challenge with appeal mills, companies that file appeals and collect legal fee reimbursements, shows how different incentive structures create different problems.

Yet the core challenges remain universal: maintaining data quality, ensuring equitable treatment, explaining our work to skeptical property owners, and adapting to technological change while preserving public trust.

Key Takeaways

For Assessors: Look beyond your borders. The solutions being developed in other jurisdictions, whether it's the Gini coefficient for equity measurement or new approaches to spatial modeling, might offer fresh perspectives on your local challenges.

For Leadership: Invest in both technology and mentorship. The most sophisticated models mean nothing without skilled professionals who understand both the math and the mission. Create environments where "eager people" can teach and learn from each other.

For the Profession: Our fundamental challenge remains constant across borders: creating fair, transparent systems that serve the public trust. Whether property taxes fund schools in Seattle or keep the sea at bay in Amsterdam, our work matters because equity matters.

The international perspective reminds us that while our systems differ, our purpose unites us. We're all trying to answer the same question: How do we fairly distribute the cost of civilization? The more we learn from each other's approaches, the better we'll serve our communities.