Friday, October 26, 2007

Lies, Damn Lies and Faulty Statistics

Mark Twain once wrote that there were three types of lies, "Lies, Damn Lies and Statistics". Statistics and numbers in themselves do not lie, the lie exists in the manner in which they are used as the following case illustrates.

By now everyone in Marion Co should have received their Fall property tax bill. Our esteemed County Treasurer, Mike Rodman, included a nice little chart of how these funds were being spent. For those of you who do not have it at hand here's a copy to refresh your memory.

According to the pie chart the % change over the 2006 levy was 100%. To me, this would mean that the levy total doubled from 2006 to 2007.

Well, it didn't, as the following table demonstrates. (click on chart to see larger image)

As you can see the actual increase in the levy is approximately 9.7 % So how did the Treasurer's office arrive at a result of 100% for the change over the 2006 levies?

They used the total Difference to calculate the change. For example let's look at the State Welfare line. The Treasurer's office calculated it as $45,732,251 divided by the total difference,
$132,382,162 multiplied by 100% to arrive at a value of 34.546% (based on the numbers included in the mailing this would be 33.567%). However, if we divide the individual difference amount by the welfare 2007 levy (which is the only way this should have been done) we get a value of 75.09% for the increase in the welfare levy. Please note if you were to try to add individual values given in the Actual % Change column together as they did with the "% Change Over 2006 Levies", you would get a result that is greater than 100%. You just can't do this, it's not mathematically sound.

Another thing to note is that if we were to ponder what the percentage the additional $45,732,251 levied for welfare is of the total 2007 levy we would find that it is 3.06 %. Not a huge increase considering the size of the levy, and yet the cost of state welfare being pushed back onto Marion Co. was cited as one reason for the need to drastically raise the tax rate.

One has to wonder whether this was a deliberate attempt to obfuscate the true numbers or just a matter of someone being mathematically challenged. Either way it does not engender a large degree of confidence in the Treasurer's office.

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