Recent posts clearly place me in the camp of “critic” for the sales tax data from Grand Forks. Criticism can be important because it encourages us to make things better, to improve upon the inadequate. With that in mind I offer up some alternatives that might be better than the current system. If we need to remove some of the “ups-and-downs” of the data, for whatever reason, let’s try to keep the some of the features of the data that keep us in the realm of informing policy. This first graph is for a long period of time and may be a bit difficult to see.
Last week I argued (here) that the city’s use of the rolling twelve month total was not really about accuracy as much as stability. Essentially the two concepts are conflated in the presentation. I still fail to see the virtues of knowing the total sales over the last twelve months, and how it better informs policy decisions. I present the following graphs to demonstrate my points about stability. Here is the monthly collection amount (recall there is approximately a two month lag between sales tax collections and the reported amount).
I used the same data that I used for the map yesterday but plotted the ratio against median total earnings. Partly this was to see if there is a pattern to discern in North Dakota counties such as higher median earnings leading to an increasing or decreasing parity ratio. To assist in this examination, I added a linear regression line and a confidence interval and this is what I found.
Today is Equal Pay Day. If you go back to January 1, 2017 and move forward from there, a woman would need to work until today, April 10, 2018, to make what a man made by December 31, 2017. That is one form of comparison. I generated the following map from Census Bureau data for counties in North Dakota for median wage by sex.
The March 2018 release came out and did not provide a ton of good news. The new data represents events of January 2018 and therefore pushes us through the entire holiday season. The March 2018 data was down 4.79% from the March 2017. The first quarter of 2018 declined 6.02% from the first quarter of 2017. The city likes to report a rolling 12 month total. For those that do not know, this means they look at the total for the last twelve months and as a new month is added they drop the oldest month. The city suggests this is more accurate, though I am not clear what the term accuracy implies here. The rolling 12-month total generally crosses multiple fiscal years so it is not really reflective of a specific budget year which would be something like calendar year accumulations. The other issue is this measure is down 19 of the last 20 months.