Hello! We are the Data Team at the Cook County Assessor’s Office. We maintain the statistical models that the Assessor uses to estimate the value of all single-family homes, small multi-family homes, and condos in Cook County, Illinois. We also build data tools to help the public understand the Assessor’s estimates and the property tax system more broadly.

Here are some useful links to tools we maintain:

• PTAXSIM: Documentation for the PTAXISM R package, which provides data and functions for running counterfactual property tax simulations in Cook County.
• Data catalog: Documentation of the CCAO Data Team’s data lake, powered by dbt.
• Open data portal: Public data that our team maintains.
• Blog: Blog posts by CCAO Data Team members.

See our GitHub page for even more links.