We love graphs because they can convey facts so well. So it’s a bit concerning that these visualizations can sometimes be used to lie to you.
A new TED-Ed video by Lea Gaslowitz walks through how, exactly, graphs can mislead you. It comes down to one basic lesson: Pay attention to the graph’s labels.
“When they’re used well, graphs can help us intuitively grasp complex data,” Gaslowitz says. “But as visual software has enabled more usage of graphs throughout all media, it’s also made them easier to use in a careless or dishonest way.”
As one example, the video points to this misleading chart that Chevrolet used in an advertisement to claim that more than 98 percent of Chevy trucks sold in the past 10 years are still on the road, far dwarfing the carmaker’s competition:
At first glance, it sure looks like Chevrolet is doing well on this score. In fact, it seems to be doing twice as well as Toyota, and far better than Nissan.
But look at the label for the y-axis. By making the graph start at 95 percent, Chevrolet made what’s actually a difference of a few percentage points seem like a much bigger deal.
To show just how misleading this graph is, check out how it would look if the y-axis started at 0 percent:
Really not much of a difference.
“This is one of the most common ways graphs misrepresent data — by distorting the scale,” Gaslowitz explains. “Zooming in on a small portion of the y-axis exaggerates a barely detectable difference between the things being compared.”
The video goes through a few more examples, showing manipulation not just of the y-axis but the x-axis and other labels too.
Gaslowitz ends with some advice: “The next time you see a graph, don’t be swayed by the lines and curves. Look at the labels, the numbers, the scale, and the context. And ask what story the picture is trying to tell.”