Back-to-back bar chart (also called divergent bar chart) is visually appealing and intriguing, I have to admit. Its shape is dynamic, capricious and unpredictable. It may look like a tree, a pyramid, a wave depending on the data set.

However, a bit shortcoming of this chart is that, it is not obvious to compare any pair of the back-to-back bars. Overcoming this will make the back-to-back bar chart a viable solution in many cases.

On 7/19/2016, the Viz of the Day or the original site is about population projection of a Swiss canton. It is based on a template from Prof. Dr. Ralf E. Ulrich's viz project. The prominent view is based on a back-to-back bar chart. It is very well designed: visually intriguing and full of information! The main problem I found is, the difference between man and women population is hard to see. And this difference is a very important piece of information.

So, I made some tweaks to remedy this problem. Again, bars in tooltips come to the rescue.

In summary, the tweaks I made are:
- changed the reference line gray scale to make the man and woman halves discernible, without changing the overall tone of the chart. Left: New; Right: Original.
- added bars in tooltips in the back-to-back bar chart to show the comparison between man and woman populations at every age.

- added action filters to highlight the view at a given age, or at a age group.
- added bars in tooltips in the summary table.

With the above tweaks, we try to bring out the information that was not so apparent to the viewers. Hopefully, this will make this chart type more useful.

Click images to go to the interactive version.