You can zero at an arbitrary point, but the point is that it forces you to explain your zero. For example, for "room temperature" you might zero at 0ºC, a value

You can zero at an arbitrary point, but the point is that it forces you to explain your zero. For example, for "room temperature" you might zero at 0ºC, a value that can be easily reached in winter. For "body temperature" you can zero at 37ºC and stretch the scale +-5ºC (aprox. the survivable range), and the graph would show fever vs non-fever. You clearly are not after some deception. For a graph of earnings or net income, you should zero at either 0T (you can have zero earnings or even negative earnings, or you can have zero income), or zero at some point that you must explain and makes sense (e.g. zeroing Boeing earnings at Boeing + MD merger). But in my experience, when someone zeros the scale at an arbitrary point, he's after a deception. I've seen graphs zeroed randomly and without explanation at 5000, and the scale going from 5000 to 5004, with the points going wildly from the top to the bottom and back again. "Wow, what a wild ride!", but in reality it was as stable as it could be. There are a lot of examples of this in business anual/quarter reports.