Does it count as a “deceptive visual” if the Y-Axis of the Column or Line Chart doesn’t start from zero?
When I was in school, the teachers will always warn us about misleading statistics and graphs created for deception.
One of the classic data visualization “tricks” that we should look out for is when the Y Axis Doesn’t Start from Zero.
For example, this.
Wow the prices of chicken rice multiplied by so much over the years?
But hey check out the Y-Axis. It doesn’t start from zero.
So it’s actually, not that much?
Is the above chart misleading? Should the Y-axis have started from zero to give a more accurate picture?
If you start from 0, you waste all this space filled up by the almost equal sized bars, as shown below:
And the chart is not as dramatic as the one that doesn’t start from zero.
The answer is another question –
What’s the story you’re telling with your data.
If you story is about the absolute value, then of course, do your data a favour, show all this bar space, and represent the prices properly with the Y-Axis starting from Zero.
If you story is about the increase in price, then, yes, there’s no need to start from zero.
That again, for trends, a line chart is the better chart to use.
And if you really want your data to show the trend and tell a truthful story, make the insight super clear that
- Prices for chicken rice increased by 20% over the last 8 years and
- In the past 1 year alone, one plate of chicken rice increased by 9%.
So, while we wait for chicken rice prices to miraculously come down again.
This should help everyone clear some doubt on the question:
Should the Y Axis Always Start from Zero