If you use graphs in your reports, please be honest in the way in which you depict your data. I wish I could embed sample charts in this post, but alas, I cannot. So please bear with me and envision the following data series: 100, 101, 102, 103, 104, etc. plotted by year.
Chart A graphs the data with the Y axis starting at 100. Chart B graphs it with the Y axis starting at zero. Charts A and B look very different; A will have a steeper slope (incline) than B. Chart B, without explanation, could mislead the reader./
If your chart’s Y axis starts at zero (for a variable like revenue that is always positive), its data will appear true to scale. Also, be sure to show Y and X (vertical and horizontal) axis value labels on your chart. This is easy to do in Excel.
In the same vein, whenever you consider a chart, be sure to understand the X and Y axis labels and scaling. If it is not explained or labelled, be careful! For example, some stock market index charts plot the logarithm of the index against time. In this scaling, the values are squashed downward relative to what the actual index values are. It makes big absolute changes in the index values look much smaller. The benefit of log scaling is that percentage changes are depicted the same: if the index went up 10% from period to period, the log of the index value goes up 10%. But the underlying changes in the amounts could have been very different if the stock market rose or fell a great deal.