## Stacked pancakes leave us empty

##### Jan 30, 2011

Reader Tyson A. serves dessert for dinner, and stacked pancakes are on the menu!

According to the St. Louis Beacons that published these charts (and more):

These pie charts take the individual states' percentages, split them up and then stack them. In this way, you can see how the proportion of taxes in each category collected by each state compares with the states around it.

This presentation fails our self-sufficiency test: one is completely lost if the entire data set was not printed on the chart itself.

The pie pieces apparently lost shape as they got stacked on top of each other. The top green slice labeled Tennessee represents 2.1% but look at the difference between the green Nebraska (40%) and the green Kansas (40.8%), for example.

Also, the red pieces and the green pieces are ordered on their own so that the Tennessee red is near the bottom of the stack while the Tennessee green is at the top.

This data can be shown clearly in a pair of line charts.

To really learn something about the data, we can create a scatter plot.

From this plot, we see that most of these states (clustered in the middle) have similar taxation policies.

The exceptions are Illinois and Tennessee, and to a lesser extent, Missouri.

I'm guessing that's the % share of the budget derived from each revenue stream? Because it can't be the actual marginal rate... if it is, I think I'll pass on moving to Missouri anytime soon!

I think bars would be better than a line, how about something like: http://public.tableausoftware.com/views/StatesPercentTaxCollected/view

Hi, I'm Brent. I created the graphic. Thanks for taking the time to discuss it.

The pie pieces only lost shape inasmuch as Illustrator distorts them when converting to 3D and scaling. I was meticulous in making sure that all the pieces were scaled and spaced identically (this is not to say that I made the best choices, only that in relation to each other, the proportions are accurate).

I think the differences between some of the slices look greater than they are because the slices aren't sitting directly on top of each other, they're spaced out (see the center point of each slice, they're all spaced evenly). I tried it directly stacked, didn't think it worked as well.

The red and green pieces are ordered on their own (from top to bottom, in ascending order of proportion of income derived from that category) for two reasons:

1) The purpose isn't to compare a state's corporate proportion with its personal proportion -- that comparison is made in the top portion of the graphic. The purpose of this portion was to compare the proportion of income each state derives from a category with other states' proportions in that category (for your readers who didn't click through, there are six categories). I think this is clear in the text introduction to that section. I only paired the categories for aesthetic reasons, the graphic would have conveyed the intended information had each category stood alone.

2) Arranging them in ascending order from top to bottom prevents a state with a small proportion from being invisible, hidden under a state with a large proportion. If Tennessee's green slice was "under" Missouri's, I fail to see how you could meaningfully show a comparison between the two: One "edge" of state's slice has to be aligned with all the others, so a smaller one will always be hidden if it's under a bigger one. It's possible there's a solution to that problem, but because it wasn't a necessity to show a smaller slice under a bigger slice, I didn't search for it.

The scatter plot is an interesting take on the data (though as a matter of accuracy, your axes are labeled incorrectly -- see note to Andrew below). As I said, it wasn't the comparison I was intending to make with this graphic, but we're planning to do more of these (there's an astounding wealth of data regarding tax income by state out there), and I'll keep it in mind.

Andrew: You have it mostly right. I'm careful to not call it the percentage share of the budget, rather it's the percentage share of tax income from each category. I suppose there may be other money in the budget not from taxes (federal grants and the like? I don't know), and I figured it was more explicit to call it what it was. I used an example in the text of the chart that I think makes it clear: "The individual income tax made up 46.1% of all state taxes collected in Missouri in 2009."

Joe: Looking at your example it occurred to me that a stacked bar might have been a solution here too.

I appreciate the discussion about the graphic and suggestions of alternate forms. It's always interesting to me how people interpret things differently, and the more I learn about that, the better the next graphic will be.

Also, fascinating blog. After being alerted to this post I've spent a while reading the archives, and I've subscribed to the RSS feed (to both blogs, actually).

The graphic looks cool, but I think the top portion of the pancakes is very confusing. The color for TN is very large but it has a very small percentage. I'm getting hungry!

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