I would have written a shorter letter, but I did not have time. --Pascal
And sometimes it's that way with data visualization, too. What starts out as a simple project--one you think will take a few minutes--gets slightly more complicated. This morning, I came across this interesting Chronicle of Higher Education story, showing Pell Institute Data on Economic Diversity. If you don't want to look at the article, here is a screen grab of the chart. Click on it to enlarge.
It's not a bad chart, but I found myself taking more time than I thought I should to figure out the story, which is that for-profit institutions enroll far higher percentages of low-income students than public institutions. (Another problem with this that I can't fix is that the data are not complete; for instance, there is no data on private Baccalaureate or Master's Institutions included in the set.) Additionally, notice the subtle changes in color when you move from the overall category to any of the institutional types. I think that can be confusing. And finally, as is the case with all stacked bar charts, it's hard to compare middle values.
The biggest problem, though, is that, there are too many things to take in at once. The story can get lost in the chart.
So I did an attempt at a quick visualization, but a small data set (seven columns by five rows) seems to make it harder to get good insight, and I spent a lot more time on this than I thought I would.
This is still not perfect, of course. For instance, it's hard to compare one institutional type to another, unless you have a good memory. But clicking the drop down box to change the type of institution shown on the bars, and comparing that to the average (orange lines) seems to work pretty well.
Let me know what you think: Does this make it easier to see the story?