Data-Ink Ratio

The data-ink ratio, an idea from statistician Edward Tufte, is the share of a chart's ink (or pixels) that actually represents data, versus ink spent on decoration. The guiding principle is to maximize it: erase anything that does not carry information — heavy gridlines, 3-D effects, redundant labels, gaudy backgrounds — so the data itself stands out.

The leftover clutter is nicknamed chartjunk, and removing it almost always makes a chart faster and easier to read. The principle is a guide, not a rule taken to extremes: a little non-data ink — a light gridline, a clear axis label, a touch of color for grouping — genuinely helps comprehension, so the real goal is a clean chart, not a bare one.