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Comment by dymk | Hacker News Reader

> There is no hard rule that all charts must have an axis at zero

Starting at something other than zero is like, the #1 thing that cable news channels do to make charts flashed on the screen for a few seconds look exaggerated.

And for a chart like the one shown in the article, there's no reason to not start at 0 unless you're trying to exaggerate the differences in values.

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>Starting at something other than zero is like, the #1 thing that cable news channels do to make charts flashed on the screen for a few seconds look exaggerated.

In this case however it is not being flashed on the screen for a few seconds, so we have plenty of time to read it and notice the axis labels, then argue in the comments that the label that we read is deceptive because people might not read it.

Also, if labelling the y axis on this graph as something other than zero is deceptive, should the x axis start at the beginning of time?

... Or show the difference more clearly. It's about visual dynamic range. Nothing wrong with it. Maybe the problem is people assuming that every x and y axes always start at 0.

Why should it start at specifically zero though? Growth can be, and often is, negative. Shouldn't it start at -50 to be sure? The point of the chart is exactly to show ("exaggerate") the difference in values!

0 is merely a convenient numerical value that also has business meaning - no growth. You can then contrast any numerical value with this, 10% meaning it grew by a fraction of .1, and so on. For most percentage quantities, it usually makes sense to start at 0 if that has some business meaning.

0.1% has business meaning, as does -1000%, for what it's worth.

Cable news channels have a problem of not labeling their axes at all, or having proportions that don't match the labels that are there. Like pie charts that show <40% as being roughly half. And then not providing enough time for viewers to fully understand the data.

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