Did you ever wonder what the Cook County equalizer is? Cook County recently announced that it’s final equalizer for 2015 is 2.6685. That means that all Cook County assessments are increased nearly 3 times before the local tax rate is applied to determine the amount of tax you pay. The equalizer is a number computed by statisticians that raises all Cook County assessments by the same amount so that it can be said that after the equalizer is applied aggregate Cook County assessments are 33% of the aggregate market value of Cook County property. It is necessary to apply an equalizer in Cook County because our assessments are so low relative to the rest of the state and school aid is based on equalized assessed values. In Cook County, homes (the bulk of the tax base) are assessed at 10% of market value and commercial property is assessed at 25% of market value. Everywhere else in Illinois, property is assessed at 33% of market value. So, the Cook County tax base is assessed much lower than the rest of the state. The Cook County equalizer raises our assessments so that after the equalizer is applied, statisticians can say that Cook County property is, in the aggregate, assessed at 33% of its market value. If you would like to see a technical explanation of how the equalizer is computed, click here.