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Shut up about the y-axis. It shouldn’t always start at zero.

If you write things on the internet, angry email is inevitable. If you make charts on the internet, angry email about those charts is inevitable. Especially if your charts sometimes use a y-axis that starts at a number other than zero. You see, an old book called How to Lie With Statistics has convinced people that truncated axes are a devilish tool of deception.

The truth is that you certainly can use truncated axes to deceive. But you can also use them to illuminate. In fact, you often have to mess with the y-axis in order to craft a useful image — especially because data sometimes reaches into negative territory and sometimes goes nowhere near zero. The right principle is that charts ought to show appropriate context. Sometimes that context includes zero, but sometimes it doesn’t. It’s long past time to say no to y-axis fundamentalism.

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