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How effective visualization brings data alive

Going overboard with simplicity

Today I look at an unlikely oversight by the New York Times:


I think they tried to simplify the scale but ended up making a mess.

Tufte preaches getting rid of all unnecessary ink but sometimes, you go overboard.


I had a tough time understanding the scale of this chart. In particular, it is hard to figure out what the numbers at the top of the chart represent since all six data labels fall into the middle of the chart. There is no vertical axis, and not enough gridlines to easily see what levels the three white lines represent. All the labelled data fall under the middle gridline. Another question is whether the vertical axis starts at zero.

So I tried drawing in reference lines (first mentally but eventually I needed them physically):


After this, it still took a few minutes to see that the gridlines were set at 25, 50 and 75% so this chart actually starts at zero. Without the axis labels, it's not clear if the vertical axis starts at zero or not! The numbers near the top of the chart are in the seventies.

I am convinced now that the individual charts share the same vertical scale. (Sometimes, putting charts on different scales is preferred, as is the case here.)


To summarize, a number of design elements were taken out of these charts:

- vertical axis and with it, the axis labels

- minor horizontal gridlines

- all data labels except the most recent numbers.

Each of these tactics, if done separately, is a best practice. All three together create a barrier to comprehension.


Finally, I should note the hybrid dot and line plot utilized here. It's a clever idea. The lines only appear when there is a rather large swing from one data point to the next, and it neatly draws attention to where the big shifts are.


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The use of lines in dot plots conventionally marks a break in the data, such as when there's a gap in the measurements or when 2 different series which are not totally comparable are plotted together. I thought that was the case here.


The question needs to be asked whether it would be better to superpose the graphs.


Yes I was going to say something along the lines of what Domingo has already said (though I wasn't aware of any convention about lines in dot plots). These lines seem to indicate survey breaks rather than big changes as such.


Domingo/Sumit: I haven't thought about the use of lines to indicate survey breaks. My interpretation of large shifts doesn't work for one or two of those charts.

I don't like the idea though - it requires that "knowledge in the head", knowing the convention; and it draws attention to the holes in the data set, rather than the data in the data set.

Ken: hard to tell unless we actually plot the superposed version.

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