Horizontal Stack!
For some reason, I can’t seem to pass up the opportunity show why stacked bar charts are usually a poor option when comparing more than one series over time.
Below is another example, taken from the last BusinessWeek edition of 2007.
If you are going to show similar data and are heart-set on a horizontal stacked bar chart, here is one tip I would recommend using the example below:
Don’t fill in the space from the amount invested series (aqua) until the percent return value (on right) with black fill. By filling the space in black, It gives the illusion that there is a third series and the total of all three amounts are exactly the same from ’03 to ’07.
I challenge you, my devoted readers, to submit an example where you think the best chart design is a stacked bar chart.
As a bonus, here is another great example where sparklines can be used to show multiple data series over time without taking up much “real-estate”. The amount of space taken up could have been a lot smaller, but you get the point; start adding sparklines to your toolkit!
