This is not a good practice at all. Do you think atmospheric CO2 charts should show 0? How about daily temperature reading for human body temperature? Should daily stock tickers all start at 0?
Why is 0 magical?
Adding 0 to the vast majority of plots shows that data at an unnatural scale that can obscure genuinely important information. Human body temperature readings on a scale from 0 to 107F would make all the important information hard to see.
A much better rule is that charts should have reasonable bounds based on knowledge of the system. For human temperature in F anything less that 95 and greater than 107 basically mean you're dead. For processes in nature good points are some delta - the lowest record to delta + highest recorded. For things like daily stock prices, a few standard deviations each way from historic volatility works.
The dogma that charts should all start at 0 is complete nonsense and tries to side step reasoning about you data. Yes scales can be used to misrepresent data, but forcing 0 to the axis does not solve this.
Why is 0 magical?
Adding 0 to the vast majority of plots shows that data at an unnatural scale that can obscure genuinely important information. Human body temperature readings on a scale from 0 to 107F would make all the important information hard to see.
A much better rule is that charts should have reasonable bounds based on knowledge of the system. For human temperature in F anything less that 95 and greater than 107 basically mean you're dead. For processes in nature good points are some delta - the lowest record to delta + highest recorded. For things like daily stock prices, a few standard deviations each way from historic volatility works.
The dogma that charts should all start at 0 is complete nonsense and tries to side step reasoning about you data. Yes scales can be used to misrepresent data, but forcing 0 to the axis does not solve this.