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Fall 2021
In The visual display of quantitative information, Edward Tuftee explains the importance of graphic integrity: “Graphical excellence begins with telling the truth about the data” (Tuftee, 2001). He analyzes a chart in order to detect its “Lie Factor” (ratio between the size of the graphical representation to the numerical quantity of the data).
To explore this principle, I selected a distorted pie chart used by the International Journal of Environmental Research and Public Health, revised on the 14th of October 2019. This pie chart is distorted because it is arbitrarily bent in addition to having a 3D edge/bevel with highlights and shadow.
“The proportion of water footprint consumed by each type of food in China
– IJERPH - 2019”
This chart is misleading, after checking the data source, the water consumption for pigs, cows, and sheep is measured in New Zealand not in China, where the cows eat pasture mostly. The paper also mentions in the introduction that “the scope, assumptions and sources of data of these country studies vary greatly and cannot be used for country comparisons” (IJERPH, 2019) but ends up doing what it shouldn’t and mislabels the chart.
Visually, the representation of the water footprint of the agriculture of pig, cow and sheep, and of eggs are put in the further part of the perspective therefore reducing the total area and angle of their according slice of the pie chart. Furthermore, the rest of the slices on the closer side of the perspective are enlarged by the perspective and the colors of the closer slices extend to the height/beveled dimension of the chart, giving them additional unnecessary area.
“The number of information carrying dimensions depicted should not exceed the number of dimensions in the data” (Tuftee, 2001), a simple flat 2D pie chart would have been a little bit better.
This chart does not represent the numbers as physically measured on the surface of the chart, “directly proportional to the numerical quantities represented”. As an additional note, the paper only looks at the water footprints of the mentioned plant-based foods from their crops without considering how much of the grain crops are used to feed chicken, and pigs, making the total water footprint of each food completely different.
Non distorted pie chart by IJERPH – 2019 of “The proportion of water footprint consumed by each type of food in China”
Another Example of Chartjunk fixed:
The next example is from a slide show about charts. This one is apparently from the Bureau of Justice Statistics. It is perfect to show what Tuftee can mean by “chartjunk”.
Youth movement in Arson - Bureau of Justice Statistics
I find the graphic misleading because the barchart metaphor starts at the bottom of the matchboxes, the reader can easily be misled by reading the length of the open part of the matchboxes as there is a misleading base line.
A clear base line is needed to remedy this. On another note, the slight perspective distortion also impacts the observed lengths of the metaphorical barchart. Finally, the additional matches outside the box misled me at first, I was not sure if it is their lengths or their quantities that represent a value for each year. To remedy these problems as I am a fan of good visual metaphors, I recreated the graph with a clear baseline using the open part of the match box as the bar, avoiding any perspective distortion and without adding any additional marks that in Tuftee’s words do not “show data”.
Remake of “Youth movement in Arson”
Sources:
The Visual Display of Quantitative Information, First edition –Edward Tuftee, 1983
Notes on Tufte’s information design principles – Pedro Cruz
Water Footprint of Food Consumption by Chinese Residents - International journal of environmental research and public health
https://slidetodoc.com/data-presentation-a-guide-to-good-graphics-bureau/
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