How about a population pyramid? That way lack of symmetry makes it clear which area grew or shrunk.

This is tough for me to absorb instantly. You are saying to the viewer, "Use one horizontal axis if the bars are black and a different one if they are red. "

I tend to think of color changes in this kind of bar chart as categorical variables, so I would use the "cannonical" depiction of flipping negative bars to the left of the vertical axis. Then way I could add another dimension of information, using your example, using color to separate software and hardware. You could still order the bars by absolute value, though it would be less pretty.

My father was color-blind and would not have been able to distinguish the black bars from the red, so I prefer the 'third way' chart.

However, to make it clearer, add another horizontal axis at the top, going from 0 at the left to 35% at the right and change the one at the bottom to show 0 at the left to -35% at the right. This emphasizes that the axis is overloaded to show all of the bars going right, with the positive ones at the top and the negative ones at the bottom.

I feel like the negative changes should be represented by negative values - positive values with a different colour is unintuitive. You could still order by magnitude of change to preserve that information.

I find when there's just two data points per category that a slope chart (basically a line or bumps chart) works best. This not only retains the original data but allows you to clearly see which are the risers and fallers, with the degree of change encoded in the angle of the slope.

http://imgur.com/a/n6vX9

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