Assessing actual Chicago real estate values is inexact science
Loop North News

The Home Front
Much of the work of the Cook County Assessor is accomplished by using digital tools. However, data used to reach an accurate assessment of your property often is not available to the Assessor in its final form.

26-Jun-22 – Assessing true real estate values in Chicago and throughout Cook County really is an inexact science and a challenge.

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.

Photo provided by Don Debat

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 instead depends 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. 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 is 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.

Cook County Government

In an effort to provide governmental transparency, 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 2022 Open Data Refresh.

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 L 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.

Fritz Kaegi

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

Kaegi, who is running for reelection, 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 most of the tax burden for decades.

Kaegi’s opponent is Kari Steele, president of the Metropolitan Water 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.

Cook County Assessor’s Office

Cook County Board of Review

Illinois Property Tax Appeal Board

Michael Griffin

• Contact Don DeBat at


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