The Data-Ink ratio is a concept introduced by Edward Tufte, the expert whose work has contributed significantly to designing effective data presentations. In his 1983 book, The Visual Display of Quantitative Data, he stated the goal:

A large share of ink on a graphic should present data-information, the ink changing as the data change. Data-ink is the non-erasable core of a graphic, the non-redundant ink arranged in response to variation in the numbers represented.

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Data-Ink Ratio - InfoVis:Wiki

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I love this term.