Jimmy Williams - Modeling, Technology and the Housing Crisis

A conversation with Jimmy Williams on valuation, neighborhoods, and the forces that shape our communities

The most powerful people in any room aren't always the ones with the titles. Jimmy Williams learned this early in his career when, as a young political intern in Philadelphia, he noticed something striking: whenever certain people called, the candidate dropped everything to answer. These weren't fellow politicians or major donors in the traditional sense. They were the people who owned the land.

"They're the people that actually have the juice and are making the decisions that affect everybody's life," Williams reflects. "They're not the candidates. They're the people that own the land."

This revelation sent Williams, now Mass Appraisal Supervisor for the City of Philadelphia, on a 26-year journey through the world of real estate valuation, a journey that has convinced him of one fundamental truth: value always flows through the land.

Beyond Dirt: Understanding Land's True Impact

When we talk about land in the assessment world, we're not talking about soil samples or agricultural yields. We're talking about location, about place, about the foundation of all economic activity. Williams puts it simply: "Every business goes back to the land."

Consider the trucking company that needs parking for its fleet. The tech startup searching for office space. Even cryptocurrency miners need physical locations for their operations. "It doesn't matter what business you're in, doesn't matter what you do, value always flows to the land," Williams observes.

This isn't abstract theory, it's the reality we work with every day as assessors. In Philadelphia alone, Williams and his team model values for nearly 600,000 parcels. Each one tells a story about how location creates value, how neighborhoods evolve, and how land ownership shapes everything from education quality to economic opportunity.

The Neighborhood Life Cycle: A Constant Truth

One of Williams' most valuable insights comes from observing what he calls the "neighborhood life cycle", a pattern every assessor recognizes but few articulate as clearly. Neighborhoods grow, stabilize, decline, and renew in a constant cycle. The key variable? Homeownership rates.

"When you have a large percentage of homeowners, neighborhoods tend to remain stable for a longer period of time," Williams notes. Philadelphia's Chestnut Hill neighborhood has remained stable for decades, anchored by high homeownership. Meanwhile, areas with more transient populations cycle through changes more rapidly.

This isn't just academic observation. Understanding these cycles helps us make better valuations, anticipate market changes, and explain our work to taxpayers who wonder why their assessments change even when their property doesn't.

The Philadelphia Laboratory

Philadelphia offers a unique vantage point for understanding urban land dynamics. As Williams describes it, the city is "still the cheapest big city in the Northeast", for now. Surrounded by Boston, New York, and Washington D.C., Philadelphia has become a refuge for remote workers seeking geographic arbitrage.

"Post-pandemic, our numbers are going up because people have the ability to work remote," Williams explains. Workers earning New York salaries while living in Philadelphia push up local values, creating both opportunity and concern. The fear? That working-class families making $50,000 annually, once able to achieve homeownership in Philadelphia, will be permanently priced out.

Technology Meets Explanation: The Modern Challenge

As modeling techniques advance, Williams identifies what might be our profession's greatest challenge: the gap between accuracy and explainability. "We're getting so good at having all of this different tech... but the public hasn't even fully accepted our multiple regression models, and now we're talking about AI."

This tension is familiar to any assessor who's had to explain their work at a public hearing. You can have the most sophisticated model in the world, but if you can't explain it to a taxpayer or city council member, its sophistication becomes a liability rather than an asset.

Williams' team has experimented with AI models, presenting their work at conferences. But he remains grounded in a fundamental truth: "Our numbers have to actually go out and people respond to it, and they actually tell us when we're right and when we're wrong."

Looking Forward: Frugality and Focus

Interestingly, Williams sees the future of mass appraisal modeling moving toward greater simplicity, not complexity. "I've looked at some models from other jurisdictions... they have so many variables and it's like at some point you're just adding things to add things."

The key is identifying what truly drives value in your specific market. What matters in Philadelphia won't necessarily matter in Atlanta or Detroit. This hyper-local nature of real estate, something every assessor understands intuitively, means our models must be both sophisticated and focused.

For those entering the profession, Williams offers advice that transcends technology: "Become a lifelong student." But he adds a crucial element often overlooked: "Read your local news." Too many professionals, he observes, get stuck in their cubicles, "not understanding how what happens in your local area impacts what you're doing."

Key Takeaways

Land as Economic Foundation: Every business, every economic activity ultimately requires location. Understanding this helps assessors see their work not as a bureaucratic function but as documenting the fundamental layer of economic value.

Cycles and Stability: The neighborhood life cycle is constant, but homeownership rates significantly affect its speed. High ownership creates stability; transience accelerates change.

The Explainability Challenge: As our models grow more sophisticated, our ability to explain them must keep pace. The most accurate model that can't be explained is less useful than a good model that can be.

Local Knowledge Matters: Technology enhances our capabilities, but understanding local dynamics, reading local news, observing neighborhood changes, connecting policy to property, remains irreplaceable.

Williams' journey from clerk to mass appraisal supervisor illustrates something vital about our profession: the best assessors combine technical expertise with deep local knowledge and the ability to see how land connects everything. In a world increasingly driven by data and algorithms, these human insights become more valuable, not less.