by David Radcliffe
Fox News recently aired a misleading attack video on President Obama. Other people have rebutted the claims made by the video, but as a math instructor, I would like to call attention to some of the misleading infographics that were used.
This graphic shows that the US public debt increased from $10 trillion to $15.7 trillion. The artist chose to represent this change by increasing the dimensions of a moneybag by about 57%. But this would increase the volume of the bag by a factor of 4, since 1.573 = 3.87. Even though the numbers are present, a visual impression is created that the debt has quadrupled.
Here is another misleading graphic which was used to show that unemployment had increased from 7.8% to 8.3%.
The relative increase in the jobless rate was about 6%, since (8.3 – 7.8)/7.8 = 0.064. But notice that the top image has 12 silhouettes, while the bottom image has 17 silhouettes. This is an increase in 42%, so the image creates the visual impression that the jobless rate has increased by 42% instead of 6%.
Why do graphic designers produce such misleading graphics? I cannot believe that they are ignorant of mathematics, but they know that dishonest graphics have more visual impact than truthful graphics. They also know that they are unlikely to be called on their distortions, because most people lack the mathematical literacy to catch them. It is vital that math instructors teach students to recognize and critique misleading infographics.