Property tax assessments of homes and commercial properties in the northern suburbs of Cook County met standards for assessment accuracy, uniformity, and equity in 2019, according to a first-of-its-kind study by the International Association of Assessing Officers (IAAO), released today by Cook County Assessor Fritz Kaegi.

The sales ratio study compared residential and commercial assessments to sale prices, and found the initial assessments met all three standards for high-quality assessments. The study also examined the effects of appeals of those assessments to the Cook County Assessor’s Office (CCAO) and the Cook County Board of Review (BOR).

“Sales ratio studies are the best way to know whether an assessment system is fair or not. The IAAO study says that our reforms lead to more accurate, uniform, and equitable assessments than in the past,” said Assessor Kaegi. “Fair assessments are the first step to ensure no one pays more than his or her fair share in property taxes. On that measure, we are delivering what we promised to Cook County taxpayers.”

The 2019 assessments were reflected in tax bills received in 2020. Based on data from the Cook County Treasurer, many 2020 residential tax bills decreased. Increases in residential tax bills averaged one percent in 2020 while commercial property tax bills increased an average of 15 percent during the same period.

The IAAO’s report is the first third-party study to review the accuracy of the 2019 reassessment process through all phases of the Cook County assessment and appeal process. Previous third-party studies of 2018 assessments showed a lack of accuracy, uniformity, and equity in both residential and, particularly, commercial assessments.

“By improving the modeling and data used in its 2019 assessments, the Cook County Assessor’s Office improved the accuracy, uniformity, and equity of its work,” said Larry Clark, IAAO’s Director of Strategic Initiatives. “The final certified values for this tax year remained within recommended ranges. This is a significant improvement on past performance.”

Throughout all levels of appeals at the Assessor’s Office and the Board of Review, 2019 assessments remained within industry standards for accuracy and uniformity. Though initial CCAO assessments, prior to appeals, met the IAAO standard for equity, the results of appeals at the Assessor’s Office showed some bias toward lower-valued properties while appeals at the Board of Review showed bias toward higher-valued properties.

“My office has published reports, data, and methodologies describing the residential and commercial assessment process,” said Assessor Kaegi. “We will continue to publish this material and invite the IAAO to study our work for a transparent look at how we are meeting the standards of fairness in assessments.”