Color coodination

Brad Delong called this "Graph of the Day", and it's been circulating in the blogosphere (Jeff Weintraub, Washington Post).

This innocent-looking thing does a good job hiding its defects.

Readability can be much improved by merely moving the subgroup labels ("All", "Democrats", etc.) to the left border of the chart.

The proportion of respondents who are Democrats, Independents and Republicans, if printed on the chart, will help us understand how the bottom three bars relate to the top one. As it is, we can reason that there were roughly equal proportions of Democrats and Republicans (the Independents are somewhat like the overall average, and the overall average is roughly at the midpoint between the Republican and the Democrat numbers).

And the colors!! Where to begin?

It used to be that color was banished from "good" graphics because it was considered unnecessary, and more trouble than its worth.  We now embrace color with moderate enthusiasm.  This chart shows why colors should be used judiciously.

If asked to provide a color key to this chart, one may come up with the following:

It appears that 8% of Democrats have been banned from wearing party colors because of their white flag on health care; ditto the 42% of Republicans who wanted health care reform.

The colors should be coordinated with the structure of the data. Here, the data has three dimensions: the answer to the question, the party affiliation, and party v. overall average.  For this graph, I reckon the answer to the question is the most important dimension.

Finally, I think by highlighting the 88% of Democrats and 55% of Republicans, the chart actually missed the information in the data: that 42% of Republicans actually supported health care reform -- my impression is that the 55/42 split among Republicans makes this a much more bipartisan issue than most other issues in U.S. politics.  In other words, the fact that most Democrats support the liberal position and most Republicans support the conservative position is just not news.

Reference: "Poll: bipartisanship popular, compromise tricky", Washington Post, Feb 9, 2010.

Comments

[alan b]

A much simpler color key would be "light grey: minority; other color: majority"

[doug]

While there are some inconsistencies, the color coding does identify the comparison that they want the reader to make (Most Dems want to "keep trying" and most Reps don't). This is really just a 3x2 table and they've color-coded the interesting cells. Given how simple the data display is (you don't need colors to understand the structure), this seems legitimate (or, at least, arguable).

[Will Stahl-Timmins]

I will also step in to defend this one. I read the use of colour here as a highlighting element, meaning: "this is the largest value of those against" and "this is the largest value of those for". Not an amazing graphic, but I've seen many worse.

To my mind, the graphic achieves its purpose of highlighting that, in general, more of the democrats surveyed answered "keep trying" than in the overall group, and more of the republicans answered "give up". It does possibly conceal the relatively large number of republicans in favour of "keep trying" at first glance, but all the information is there if the reader wants it.

[Kaiser]

Will: it's not a horrible chart by any means. I'm pointing out a small detail which may have escaped their attention. One could interpret the colors as calling out the salient parts but as I wrote in the last paragraph, those are NOT the important parts of the chart. Think about the same chart for most other political issues: abortion, the war, deficits, social security, etc. All charts would look the same: each party's supporters support their party's position overwhelmingly. The salient issue for health care is the less extreme than normal split on the Republican side.