This is absolutely atrocious stuff - if dodged bars are hard enough to get information out of, why would you add a separate bar, in a different shade, which possibly has different units (percentage versus percentage points?)?
The best way I would think of showing this information is a slopegraph, where for each category, you’d see the level in 2015 and level in 2017, and a line connecting the two, and the slope of that line (also possibly coloured) can indicate the degree of change.
Even a labelled scatter plot would be okay to show this data. It seems like the maker of this graphic chose the worst possible way to show the data
Source: https://twitter.com/CathyYoung63/status/1038632265272705025











