Because it never cost 0. It's usually wrong to set the y-axis to 0. The whole point of a graph is to illustrate the change that you're talking about. Imagine a

Because it never cost 0. It's usually wrong to set the y-axis to 0. The whole point of a graph is to illustrate the change that you're talking about. Imagine a graph of global temperature, for example, where you decide to use Kelvin. Set the y-axis to 0 and look! There's no noticeable change at all. Global warming is a myth! You should set the y-axis so it shows the normal variation and then you can see if recent changes are outside of that.