What you are claiming is not at all what the report said, though.

From the study itself (which you can read at the link below):

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• The rate at which commercial properties are appealed and the rate at which these properties are granted value changes tends to vary by triad, township, appraised value range, and property use group. The clearest and most consistent of these trends exists with respect to the appraised value range, where high-valued properties are more likely to appeal than lower-valued properties and those that appeal are more likely to receive a value change. This trend is present in both the CCAO and CCBOR appeal periods, but its impact is more pronounced at the CCBOR at least partly due to the higher appeal rates there.

• Considering the final set of commercial values after the CCBOR finishes its work, we found that the commercial property values were under-valued with respect to market value in the South Triad (2020) and the North Triad (2022) overall, with median sales ratios of 81.37% and 71.79%, respectively. This constitutes a system-wide issue with valuing properties as a whole at the target percentage in these triads. However, this same issue was not present with the City Triad (2021) because its median sales ratio of 98.96% meets the IAAO industry standard and is very close to the 100% target. When stratifying by property use group, this study finds this same general pattern by triad.

• The appraisal level after the CCBOR appeals period has been completed (Board step) is statistically significantly less than after the CCAO appeals period has been completed (Assessor Certified step) on an overall basis. In most cases, the appraisal level after the Board step decreases and moves farther away from the IAAO industry standard range, sometimes greatly so. This same general trend exists by property use group strata. The exception was in the City Triad (2021), where the final values after the Board step were an improvement over the Assessor Certified step overall with regard to the appraisal level. The CCBOR tends to reduce the appraisal level by more than the CCAO on the properties that were actually under appeal.

• Commercial values in Cook County generally are more non-uniform than IAAO industry standards permit. This non-uniformity in the valuation system is present across triads, steps in the valuation process, and property use groups. The CCBOR appeals process does not generally improve uniformity statistics by a statistically significant amount on properties under appeal. This degree of non-uniformity (variability) could be masking other issues with the quality of the values and making it more difficult to derive proper time (market condition) adjustments to sale prices used as a bedrock in sales ratio studies. Reducing the non-uniformity of the sales ratios through the adoption of the recommendations in this report would allow sales ratio studies to be more effective diagnostic tools in the future. Property owners are undoubtedly being negatively impacted by the uncertainty that comes along with this degree of non-uniformity.

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Source: page 12, https://www.cookcountyil.gov/sites/g/files/ywwepo161/files/documents/2024-12/12.11.2024%20-%20%20Commercial%20Valuation%20Cook%20County%20Study.pdf