GIS/ValTech 2027

This presentation examines the core assessment issues of uniformity, valuation, and taxpayer impact through an interactive mapping case study spanning ten years and 1.8 million parcels in Cook County, the second-largest assessment jurisdiction in the United States. The scale of the data presents significant analytical challenges, including outliers, classification complexities, and changing valuation patterns.

The study revisits the foundational work of Homer Hoyt, whose 1933 landmark analysis, starting in 1830, linked Chicago land values to race, rents, income, and urban growth. It also builds upon the research of Gabriel Ahlfeldt and Daniel McMillen, who documented how transportation, economic change, and neighborhood density influenced land values between 1913–2010.

By comparing Cook County land valuations from 2016–2025 with studies spanning 1830–2010, the presentation identifies major divergences in land-value patterns across centuries. It explores the practical implications of assessment policies and taxation shifts in Cook County, Illinois, the second-highest property tax jurisdiction in the nation with the highest tax delinquencies and increasing land-based appeals. Cook County’s 30 miles of Lake Michigan shoreline includes some of the most valuable urban and suburban land in the Midwest. Land value now represents an increasingly significant component of property assessment, creating new challenges for assessors, taxpayers, and assessment professionals.

The study leverages customized proprietary software, QGIS, and other GIS tools to analyze assessment characteristics, land values, and spatial patterns. We demonstrate why assessors, assessment and legal professionals should develop their own land valuation analysis, visualization tools, using open-source and in-house technologies.

Andrea Raila, Senior Tax Analyst, Raila & Associates - IL

Keywords: GIS & Spatial Analysis, Assessment Equity, Mass Appraisal & Valuation Modeling, Beginner