How do TIFs impact municipal tax bases?

Tax Increment Financing (TIF) freezes a district's taxable value and diverts the growth above that base into a redevelopment fund. Overlapping agencies such as school, park, and library districts and the municipality itself must then levy against a smaller base, so their rates go up.

This memo identifies the five Cook County municipalities outside Chicago with the highest share of parcels inside TIF districts: Phoenix, Bedford Park, Bellwood, Ford Heights, and Posen. It then traces each one's frozen base against its TIF increment from 2006 to 2023. Comparing actual effective tax rates with a counterfactual in which the increment stayed in the base shows how much of each rate is TIF-induced. In Phoenix, where 98% of parcels sit inside a TIF, the 2023 rate of 2.05% is nearly 46% above its 1.40% counterfactual. Across all five villages, park districts and municipalities bear the heaviest rate inflation.

Originally started during an internship with the Cook County Assessor's Office (CCAO), Jan–Mar 2026. Subsequently developed and extended independently. Not an official CCAO work product.

From the repository · rushikeshay/tif-districts-analysis-ccao-project

Key Methods

• Geospatial analysis using sf
• Data wrangling with dplyr and data.table
• Interactive visualization with plotly
• Spatial mapping with ggspatial
• Property tax data processing using ptaxsim
• API ingestion using httr and jsonlite

Key Outputs

TIF Concentration

• Share of PINs within TIF districts by municipality
• Identification of high TIF-penetration municipalities

Property Value Dynamics

• Time series of total EAV vs frozen base
• TIF increment growth across municipalities
• Cross-city comparison (Phoenix, Bedford Park, Bellwood, Ford Heights, Posen)

Effective Tax Rates

• Actual vs counterfactual tax rates
• Estimated rate inflation due to TIF base reduction
• Agency-level decomposition (school, municipal, park districts)