Tufte's writing is important in such fields as information design and visual literacy, which deal with the visual communication of information. He coined the term "chartjunk" to refer to useless, non-informative, or information-obscuring elements of quantitative information displays. Other key concepts of Tufte are the lie factor, the data-ink ratio, and the data density of a graphic.
He uses the term "data-ink ratio" to argue against using excessive decoration in visual displays of quantitative information.In Visual Display, Tufte states:
Sometimes decorations can help editorialize about the substance of the graphic. But it's wrong to distort the data measures—the ink locating values of numbers—in order to make an editorial comment or fit a decorative scheme.
Tufte also encourages the use of data-rich illustrations with all the available data presented. When examined closely, every data point has value; when seen overall, trends and patterns can be observed. Tufte suggests these macro/micro readings be presented in the space of an eyespan, in the high resolution format of the printed page, and at the unhurried pace of the viewer's leisure. Tufte uses several historical examples to make his case including John Snow's cholera outbreak map, Charles Joseph Minard's Carte Figurative, early space debris plots, and Maya Lin's Vietnam Veterans Memorial. For instance, the listing of the names of deceased soldiers on the black granite of Lin's sculptural memorial is shown to be more powerful as a chronological rather than as an alphabetical list. The sacrifice each individual made is thus highlighted within the overall scope of the war.