80  Data-Ink Ratio

Edward Tufte also strongly advocates maximizing the data-ink ratio. The data:ink ratio is the ratio of data ink to total ink and considers how much ink is actually necessary, as opposed to being decorative. In short, the amount of non-data ink should be minimized. This is in line with classic design principles of less is more and simplicity, however there doesn’t appear to be any emperical support that removing non-data ink aids in visual communication. In my experience, plots with a high data:ink ratio do tend to look more professional and are more appealing. My approach is not as extreme as Tufte, who is quite ruthless, removing even axis lines. I advocate uncluttered and simple charts as opposed to minimal charts.

Every element on your plot (data and non-data) has to justify its presence

Small multiples separate each sub-set into its own plot, making it easier to see individual trends.

The advantage of reducing the information content on each facet is that we now have room to add more interesting variables. In this case, we can add information on the regression line and correlation coefficient.