Also from Consumer Strategist magazine comes the following chart about "PotatoPacks". (To their credit, the magazine uses a lot of charts, nost of which are completely harmless.)
This is a good example of what Tufte calls a low data-to-ink ratio. There are exactly 10 pieces of data on this chart, the number of potato packs and the market share for a five-year period.
Much resources have been thrown at the problem of showing growth: it's a surround-sound treatment with loud speakers. The potatoes, the gridlines, the axis, the data labels. And yet, it's unclear what the message is.
According to the title, "both sales volume and market share have steadily increased since the introduction of the PotatoPack." It would have been a very nice touch to add a little arrow letting us know when PotatoPack was introduced. Was it in 2006 the starting point of the data set? Or was it in 2007 when the sales volume started to increase?
There is an unintended message. It's that all potatoes are not born equal!
Take a look at the two stacks labeled 572 and 493. How is it that 572 gets us 4 potatoes, and 493 gets us 3 potatoes? So for 2006, each potato is worth 143 packs while in 2007, it's worth 164 packs.
For 2010, they plotted projected data, which is exactly how it should be done.
The following chart shows the year-to-year growth rate of the PotatoPack sales relative to the growth rate of the entire market. This may be the more interesting aspect of this data set.