Chapter 7 of Berinato’s Good Charts, focuses on ‘”the blurred edge of truth” or the line between visual persuasion and visual dishonesty. The chapter starts off with a scenario between a boss and employee. The boss asks the employee to create a chart and they end up disagreeing. Berinato then uses this as an introduction to his argument. First he touches briefly on the persuasion techniques. These include emphasis, isolation, and adding or removing reference points. The 4 types of deception include falsification, exaggeration, omission, and equivocation. The main topic of the chapter is the balance between the gray area. The chapter outlines the common techniques used that put charts in the gray area. Some of these techniques include the truncated y-axis, the double y-axis, and the map. Throughout the chapter different graphs are used as examples to display visual manipulation or the borderline of truthfulness and dishonesty.
Berinato makes the metaphor that persuasion is like a knife. The knife can be used skillfully, recklessly, or illicitly. Figuring out ways charts slip in deception is equivalent to handling a knife without cutting anyone. The first technique that is discussed is the truncated y-axis. This technique removes valid ranges from the y-axis and removes data from the visual field. It emphasizes change but it can also exaggerate and misrepresent change. The second technique is the double y-axis. It includes 2 vertical scales for different data sets in the visual field. This technique compels the viewer to make a comparison to sets that don’t naturally go together, but the relationship between the 2 could be artificial. The third technique is the map, which uses geographical boundaries to encode values related to that location. It allows easier access to see trends at local, regional, and global levels, but the size of a region does not necessarily reflect the data encoded within it. Berinato states that these trends help judge whether your graph crosses the line between manipulation and persuasion. Another way to judge is to imagine someone challenging your graph. You should have supporting evidence to challenge a counter. Basically when creating a graph, try to find a balance between persuasion and honesty, without being manipulative.