Request for Timely Publication of 2026 "Mailed" Assessed Values to Open Data Portal

[dilemmamanagement]

General description

Following up on our discussion in issue 41 from last year regarding the refresh frequency of the Assessor Historic Assessed Values dataset.

Use case

The Blocker:
I followed your advice and explored the Data Subscription Service. However, after reviewing the 2026 Agreement, the terms strictly prohibit "derivative works" and "external commercial use," which effectively bans any modern data science/AI application from using that feed. The subscription is legally designed for internal reference only, not for building tools for homeowners.

The Consequence:
This leaves the Open Data Portal as the only viable mechanism for public-facing tools to access current timely assessment data.

The Request:
Currently, there is a "Time Gap" between when notices are mailed and when the Open Data Portal is updated (monthly). This creates an information asymmetry where only those with legacy access can see the new values during the critical appeal window.

Is it possible to automate the ETL to trigger an update to the Mailed Assessed Value columns (assessor mailed building value, assessor mailed land value, assessor mailed total value) in the Open Data Portal on the same day a Township opens for appeals?

Thank you for your work on open data!

Universe

Existing dataset: https://datacatalog.cookcountyil.gov/Property-Taxation/Assessor-Historic-Assessed-Values/uzyt-m557

Unit of observation

Existing dataset: https://datacatalog.cookcountyil.gov/Property-Taxation/Assessor-Historic-Assessed-Values/uzyt-m557

Restrictions and exclusions

NA

Data delivery format

Open Data asset

Citation and use of Assessor data

• I agree to the above terms.

[ccao-jardine]

Hi @dilemmamanagement , thanks for engaging with us and our Open Data assets. Sorry that I steered you wrong in the data subscription service; I didn’t know that was part of the agreement.

We can’t establish and guarantee an Open Data refresh schedule that is timed with reassessment mailings. Please reach out to our Chief of Staff to escalate this further at Scott.Smith (at) cookcountyil (dot) gov.

In data science transparency news, we did build the Home Value Report last year. Check it out!

https://www.cookcountyassessoril.gov/home-value-report

Repo: https://github.com/ccao-data/homeval

[dilemmamanagement]

Hi @ccao-jardine. Thanks for sharing the home value report; I will take a look.

Could you provide the rationale for not updating the file that the data team generates in a timely manner? Is it possible to update the file within a week from each township appeal open date?

I appreciate the re-route to chief of staff and will chase it as i have other reasons (e.g. a year old FOIA still not addressed). But in an election year I would think being transparent and timely in the assessed values that are generated by CCAO is important.

[ccao-jardine]

Hi @dilemmamanagement, just wanted to let you know that we're testing updating our Open Data assets (like the requested Assessed Values data) to refresh twice as often! It just refreshed today.

[dilemmamanagement]

Hi @ccao-jardine . This is amazing. Thank you for providing the 2026 assessed values as soon as possible.