Pyramid charts look a lot more attractive than bar graphs, which presumably explains why Office's charting option includes so many of them. However, their visual appeal shouldn't blind you to the fact that they often misrepresent data.
The Stubborn Mule blog dismantles a recent infographic used to discuss whether US food policy indirectly results in America's chronic obesity problem. As the site points out, the use of the pyramid format produces an inaccurate picture of the actual information:
The problem is that the data is represented by the height of each segment of the pyramid, but we tend to perceive the apparent volume of each layer. As a result, the layers near the top appear much smaller that they should relative to the lower layers.
Indeed, the blog makes the case that when it comes to charting, less is definitely more and those :
I would argue that everything below “2-D Column” [in Excel]should be banned from the arsenal of the thinking chart-user. These variants on three-dimensional graphics all represent the trap “chart junk”: fancy extra details that, at best, add nothing to the information being conveyed and, at worst, result in distortion.
I don't doubt some people choose fancy charts for exactly that reason — visual distortion is a neat trick to conceal data you don't want your boss to see. It's still dishonest, however, and if your aim is to be accurate, it's definitely time to rethink those chart types.
Check the whole post for more discussion of which chart types best suit different types of data, and tell us your own favourite charting techniques in the comments.
Pyramid Perversion – More Junk Charts [Stubborn Mule]