We make a lot of charts at Vox.com.
And, of course, charts have axes.
And pretty much every time we make a chart
with a y-axis that starts anywhere other than
0, someone winds up emailing to complain.
You see, there's a very famous book called ‘How to Lie With Statistics’
and it contains a discussion of how you can create
a misleading chart by messing with the y-axis.
And it’s definitely true that you can do
this.
Here's a chart from Fox News, for example. It's a total disaster..
But the y-axis dogmatists take it way too far.
The big problem with people who lie with statistics
is that they are trying to lie to you.
It’s true that misleading charts are one
way to lie.
But the English language is also a tool that can be used for lying, and that doesn’t mean we should
never speak English.
Sometimes you need to fiddle with the y-axis
to tell a story properly.
Right now, for example, the share of American
adults who have a job has fallen to a generation-long
low.
This is a really big deal.
But if you chart this data with a y-axis at 0,
you can’t see the change at all.
Narrowing the range to dramatize what we’re
talking about isn’t “lying” with statistics.
It’s emphasizing what’s relevant.
The way Edward Tufte puts it is you need to “use
a baseline that shows the data, not the zero
point.”
After all, 0 is just a number like any
other.
Sometimes to make sense of the data, you need
to be able to show numbers that go below 0.
Halting at 0 in those cases just doesn't make any sense. But extending every chart way below
0 would be crazy, too.
And of course where 0 even is depends on the
units you are using.
If you do a chart of a person’s temperature in
Fahrenheit, you’re likely
to miss the fever if you’re zoomed all the
way out to 0.
But if you redo it as a Celsius chart, it’s
not quite as bad.
But if you switch to Kelvin and extend everything
to Absolute Zero then your charts become useless.
When people are really lying with charts,
the main thing they’re normally doing wrong
is leaving out the context, not leaving out
the 0.
Now back to that Fox News chart.
You would never know from this chart that
the top marginal rate was 39.6 percent back
in the Clinton administration.
Or that in the first half of the Reagan administration
it was 50.
Or that back when Eisenhower was president,
it was 91.
The missing 0 was really the last of that
chart’s problems.
They left out the entire history of taxes
in the United States.
So just remember, y-axes don’t lie to people.
People do.
