data-ink ratio

Here’s a wiki post about Edward Tufte’s data-ink ratio:

Tufte refers to data-ink as the non-erasable ink used for the presentation of data. If data-ink would be removed from the image, the graphic would lose the content. Non-Data-Ink is accordingly the ink that does not transport the information but it is used for scales, labels and edges. The data-ink ratio is the proportion of Ink that is used to present actual data compared to the total amount of ink (or pixels) used in the entire display. (Ratio of Data-Ink to non-Data-Ink).

Good graphics should include only data-Ink. Non-Data-Ink is to be deleted everywhere where possible. The reason for this is to avoid drawing the attention of viewers of the data presentation to irrelevant elements.

The goal is to design a display with the highest possible data-ink ratio (that is, as close to the total of 1.0), without eliminating something that is necessary for effective communication.

Before I offer an opinion,  I should state the disclaimer that you should definitely listen to Edward Tufte, not me! So here’s my opinion: this idea is clearly absurd when taken to extremes because it would just mean a bunch of dots on a page that you have no way of interpreting. I can’t think of a way of making graphs without axes, scales, and a legend. Labels, arrows, and text boxes are an alternative which I find myself using often when giving projected slide presentations in fairly large rooms.

A reasonable interpretation of Tufte, I think, is to ask yourself whether each new thing you are adding to a graph provides useful information to the reader/viewer, increases the chances that the reader/viewer will draw the right conclusions, and makes the reader/viewer’s job easier or harder. The holy grail is to help your audience imbibe the point of the graph with very little effort. Unnecessary 3D effects and clip art aren’t going to do that. A splash of color and some nice big labels that middle aged people can read from the back of the room just might help.

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