How Charts Lie

Starred review from August 26, 2019
Visual journalism professor Cairo (The Truthful Art), who has consulted for Google and the Congressional Budget Office, provides a valuable guide to reading charts with a critical and nuanced eye. With the use of such graphics throughout media only increasing, Cairo insists, persuasively, that “just looking at charts, as if they were mere illustrations,” is not enough; “we must learn to read them and interpret them correctly.” After offering a guide to different kinds of charts, Cairo presents the different ways they can mislead, including by using the wrong data or concealing uncertainty. His examples of misleading charts include one from an antiabortion group purporting to show Planned Parenthood’s cancer-screening and prevention services sharply declining while the abortions it provided sharply rose; Cairo patiently explains how the chart concealed and distorted information, such as by “using a different vertical scale for each variable.” By also criticizing staunchly liberal New York Times columnist Paul Krugman for using a chart depicting the annual U.S. murder rate that omits data from more recent years, Cairo even-handedly demonstrates that the misuse of infographics is not confined to one political side. At a time of widespread concern over disinformation in the media, Cairo provides a valuable corrective to the acceptance of numbers, and their visual representation, as having objective truth.

September 1, 2019
As this entertaining addition demonstrates, the "how to lie with statistics" genre is alive and well. Cairo (Chair, Visual Journalism/Univ. of Miami; The Truthful Art: Data, Charts, and Maps for Communication, 2016, etc.) points out that "charts may lie...because they display either the wrong information or too little information. However, a chart can show the right type of information and lie anyway due to poor design or labeling." In a cheerful introductory chapter, the author explains that, while writing was invented about 5,000 years ago and charts weren't used until the late 1700s, both are encoded forms of communication with a structure and vocabulary. Readers receive well-researched information about the makeup of a chart along with the warning that this knowledge, like rules of grammar, is necessary but not sufficient. It's essential to pay attention. Cairo begins with a U.S. map, almost entirely red, that many claim shows the overwhelming popularity of Donald Trump in 2016. But how could that be if he received only 46 percent of the vote? The trick is that the map label shows not voters but counties with Trump majorities. Since large counties (rural) mostly voted for him and small counties (urban) didn't, such a map is overwhelmingly red. The map, although real, is used to lie. In the generously illustrated chapters that follow, the author delivers a painless, if often uncomfortable education. On a trivial level, one must know what a chart is measuring. A chart of homeless schoolchildren in Florida reveals counties with more than 20 percent. The streets are not full of sleeping students because "homeless" is not defined as "no home" but rather as "lacking a fixed, regular nighttime residence." There are plenty of no-brainers, sadly widely ignored, such as, "correlation is not causation." The graph showing that cigarette smoking increases in nations with a greater life expectancy does not prove that smoking is healthy. An ingenious tool for detecting flaws in charts, which nowadays seem mostly deliberate.

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