Coefficient of Dispersion . . . . . What
How do we judge the Assessor's job? Well, the Township Assessor
must certify the assessed valuation of each and every parcel in
the Township. This certification is reported to the McHenry County
Supervisor of Assessments and used to create your tax bill. There
are over 18,400 parcels in Nunda Township.
How do we measure
the Assessor's performance? We measure it “statistically”.
There are basically 2 statistics that we need to measure. How close
to the statutory 33 1/3% of fair market value are the Assessments;
and how uniform are our assessments.
The most commonly used statistical measure of assessment uniformity
in a ratio study is the COEFFICIENT OF DISPERSION (COD).
The COD provides
a measure of the variation of individual assessment ratios around
the median level of assessment. It can be stated as the “average error” expressed
as a percentage. The lower the rate of dispersion, the more uniform,
and fair the spread of the tax burden. To put it another way,
there should be some uniformity in the assessment of all the
homes in your neighborhood, even if they don't look exactly like
The COD actually measures that uniformity; or lack of uniformity
in statistical terms.
Once we calculate the median, or the middle, we can determine
how wide are the variations from the median. How fair is your assessment
as compared to your neighbors? We calculate this variation on a
Township wide basis, neighborhood by neighborhood.
What is this “Median Level of Assessment”? Well we all know the
state statute says the assessed valuation of your home should be
33.3% of fair market value. The fair market value can only be determined
by a sale. So, we list the sales, divide each sales price by the
Assessed Valuation and see how close they all came to 33.3%. How
wide are the variations from the median, or middle? How “uniform” are
our assessments. . . . . What is our Coefficient of Dispersion
? To put it another way. What is the average deviation?
Assume a township has a median level of assessment of 30% and
a Coefficient of Dispersion of 40%. The assessment levels of individual
properties on the average can be expected to deviate plus or minus
40% from the middle. Assume two similar properties had a market
value of $90,000. One could be assessed at 42% and the other at
18%. Given a tax rate of 6%, one property tax bill could be $972
while the other $2,268. The tax burden is not shared equally in
You can see how important assessment uniformity can be. Each Township
Assessor strives for a low COD. The lower the COD, the smaller
the Average Deviation.
Our County Supervisor of Assessments considers any Township under
15% to be good and any Township over 20% to be bad. Adjustments
to the Township Assessors books or even rejection may be the result
of a high COD.
Now lets see. . . . . How did Nunda Township do last year! Dennis
Jagla and his staff got an over all score last year of 10.37%.
One of the very best in McHenry County. His median level of assessment
was also very close to 33.3%. The Nunda Township Assessor's office
is a fully computerized office with 5 professional staffers doing
a big job well. KEEP UP THE GOOD WORK DENNIS!