Equalization

Equalization Factors

2025 SA Equalization Factors
Cherry Valley	1.1055
Durand/Laona	1.1073
Harlem	1.0996
Owen	1.1140
Pecatonica/Seward	1.0741
Rockford	1.1143
Rockton	1.0928
Roscoe	1.0949
Winnebago	1.1106
Shirland/Harrison/Burritt	1.1185

Equalization Factors 2006 through 2024
Illinois Department of Revenue - Publication 136 - Property Assessment & Equalization

Equalization is the adjustment of the median level of assessment up or down so that the tax burden is "equalized" among taxing districts.
State law requires equalization in order to bring assessments to the level required by state law, which is 33.33% of fair cash value.
Equalization is accomplished by the use of an Equalization Factor, which is a factor applied to all non-farm assessments.
Equalization factors can occur at four levels:
- Neighborhood level, as applied by the Township Assessor.
- Township level, as applied by the Supervisor of Assessments.
- Township level, as applied by the Board of Review.
- County level, as applied by the Illinois Department of Revenue.

Gather the Data.
Real Estate Transfer Declarations from 2016, 2017, and 2018 (from form PTAX-203)
Assessment Data from 2015, 2016 and 2017 (from Board of Review's Equalized Assessed Values).
2018 Assessment Books (from Board of Review's Certified Assessment Roll).
2019 Assessment Books (from Township Assessor).
Conduct a Three-Year Sales Ratio Study.
Compare 2016 sales to 2015 Assessed Values.
Compare 2017 sales to 2016 Assessed Values.
Compare 2018 sales to 2017 Assessed Values.
Calculate the median level (the point at which half of the data is greater, and half is lesser after trimming outliers) of assessment for each year.
Calculate the Projected Equalization Factors.
Adjust each year's median sales ratio to reflect the changes made in the level of assessments (for each township).
For this example, the 2016 ratio was 30.91%; the 2017 ratio was 31.21%, and the 2018 ratio was 32.67%.
The level of assessment (33.33%) is divided by the average of the adjusted ratios to establish the 2019 Projected Township Equalization Factor.
Example
               2016 Adjustment is 30.91% x 1.0279 = 31.77%
               2017 Adjustment is 31.21% x 1.0279 = 32.08%
               2018 Adjustment is 32.67% x 1.0279 = 33.58%
               Sum of the Adjusted Factors is 97.43%
                                                                         ÷ 3
                                                                     32.48%
                33.33% ÷ 32.48% = the Township Factor:        1.0262
Apply the Equalization Factors.
This process is conducted for each of the 14 townships in Winnebago County.
The assessments in each township are adjusted by that township's equalization factor to provide an Equalized Assessed Value (EAV) for each parcel.
The equalized assessments are then certified to the Board of Review
Example:
A property in the township used in this illustration with an assessed valuation of $100,000 would have an equalized assessed valuation of $102,620.
($100,000 x 1.0262 = $102,620)

Equalization

Equalization Factors

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