Back in the early 1980's, when the legislature passed the law that an estimated fair market value be included on all tax bills, was a time across Wisconsin when Assessors for the over 1800 municipalities were not required to assess property at market value during any time interval. As a "truth in taxation" measure, the legislature thought it was important for their constituents to know what in terms of value their assessment actually meant. Because the DOR already prepared municipal "equalized values," the legislature thought that these estimates made at the municipal level should be provided at the property level. This was an easy answer to their problem.
Remember, the intent was to show whether the assessment on a property was at all accurate. It was never meant to actually be your individual property estimate. But, at least from the taxpayer's standpoint, it meant more than the assessment--at that time. For instance if the assessor was assessing property in your municipality at 10% (and you had no idea of that fact) and your tax bill showed an assessment of $10,000 you might think "boy am I getting a good deal--I know my house is worth at least $60,000." However, if you realized that the $10,000 actually equated to approximately $100,000; you might not be so happy. (Since 1986, after this was enacted, the legislature tightened the law and we now are required to assess within 10% of market value at least once in every four year period.)