The general duties of a township or multi-township assessor include the assessment of all real property, with the exception of operating railroad property and certain pollution control facilities in their jurisdictions, as of January 1 of each year.
By Illinois Statute, the assessment of all nonfarm real property is to be based upon its fair market value as of January 1 of each year. Fair market value is generally considered to be the price the property owner could expect to receive for it if it were sold on January 1 of that year. In Illinois all nonfarm real property is to be assessed at 1/3 of its fair market value. While a good portion of each assessor's job is to equally distribute the tax burden throughout their jurisdiction by the use of good assessment practices, an assessor does not determine taxes nor do they raise or lower taxes. They only estimate the market value of all nonfarm property in their jurisdiction and assess it accordingly.
In arriving at an assessment, an assessor uses accepted appraisal techniques. However, instead of dealing with single properties such as a fee appraiser working for a lending institution, a township or multi-township assessor practices the art of mass appraisal. This means that instead of appraising single properties, they must appraise a universe of properties within their jurisdiction. Not only do they assess all those properties that have been sold, they must also assess those that have not sold; determining the probable market value or sales price of those properties. Oftentimes this involves second guessing a buyer or seller's motivation, predicting what will happen to the real estate market in their area, and, perhaps most difficult of all, guessing rather or not a property has a certain appeal to a potential buyer that will cause him to pay more for that property than another someone else.
When assessments increase in general, it shows properties are underassessed. When assessments in certain areas increase it indicates those areas were underassessed and not paying their fair share of real estate taxes, thereby putting an unfair tax burden on other properties in the general area. The fact that certain properties show a greater assessment increase than others in a reassessment shows that those properties were dramatically underassessed in the past and not paying their fair share of real estate taxes, thereby putting an unfair tax burden on everyone. Conversely, those properties whose assessment decreases after a revaluation were over assessed and were paying more than their fair share of real estate taxes.