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Assessing Chicago’s True Real Estate Values Is A Challenge

Assessing true real estate values in the city of Chicago and throughout Cook County really is an inexact science and a challenge.

Fritz Kaegi

Cook County Assessor Fritz Kaegi readily admits his field team, which helps maintain residential characteristics on 1.2 million properties, legally cannot enter homes and so “must make educated guesses” as to interior features, improvements and appointments.

Who knows how many thousands of Chicago homes and two-flats have basement, attic, garage and coach-house apartments with illegal kitchens and bathrooms that date back to before the end of World War II?

The Assessor’s team readily admits it cannot be realistically staffed to knock on every residential property door in Cook County every year and depend on home-improvement permits to trigger site visits.

“Permitting is at best an incomplete process—some home improvements are performed unpermitted, and some permits do not accurately represent the work being done,” according to a new “Open Data Portal” recently opened by the Assessor.

Much of the Assessor’s staff work is accomplished by utilizing digital tools, including the “Automated Valuation Model” (AVM).

The AVM is joined with the “parcel universe” to allow convenient spatial analysis and mapping of sales, which can be joined to historic assessed values for ratio studies, notes the Open Data Portal.

Got that?

So, it’s no wonder that Assessor Kaegi says his data department cannot currently guarantee that historic and current parcel values align with what is presented on his website.

Therefore, the data used to reach an accurate assessment often is not available to the data staff in its final form. “We hope to be able to confirm the accuracy of data we’re making available here against what’s available on the website soon,” according to the Open Data Report.

In an effort to provide governmental transparency, Assessor Kaegi recently published millions of rows of data on Cook County’s Open Data Portal. Datasets from the Assessor’s office can be viewed and downloaded online at:

The data for each property contains the following:

  • Assessed values from 1999 to 2021.

  • Transaction and sales data.

  • Location data, such as the school district in which the property is situated, and distances to amenities, including the nearest El station or park.

  • Physical characteristics of homes and condominiums.

These datasets will automatically update periodically with new information as it is entered into “iasWorld,” the Assessor Office’s modernized assessment system of record.

“Since the start of my administration, I’ve prioritized transparency and data integrity,” Kaegi said. “The publication of this historic assessment date demonstrates my dedication to these values.”

Assessor Kaegi, who is running for reelection on June 28, has been targeted and criticized by big commercial property owners and apartment developers for refocusing assessment efforts on them—and away from homeowners, who have been carrying the majority of the tax burden for decades.

Kaegi’s opponent is Kari Steele, president of the Metropolitan Reclamation District of Greater Chicago.

Property owners who think they are over assessed should file an appeal, advises expert property tax-assessment lawyer Michael Griffin.

Visit the assessor’s website:, or call 312-443-7550 to find comparable properties or start the appeal process.

A taxpayer can file with the Cook County Board of Review (312-603-5542) or and later with the Illinois Property Tax Appeals Board (217-785-6076), or Or, call Michael Griffin at 312-943-1789.

For more housing news, visit Don DeBat is co-author of “Escaping Condo Jail,” the ultimate survival guide for condominium living. Visit


“The book is Escaping Condo Jail by Sara Benson and Don DeBat. I would say that anybody thinking about buying a condo, or even anybody serving on a condo board, or anybody who has any connection to a condo, this is must reading—all 600 and something pages. Thanks a lot for a great book!”


Steve Sanders, “Your Money Matters” WGN TV, December 22, 2014

By Don DeBat

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