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  • Tammy LaBiche-Henley thinks this is interesting:

While we’re considering lengths of bars, let’s also spend a moment on the width of bars. There’s no hard-and-fast rule here, but in general the bars should be wider than the white space between the bars. You don’t want the bars to be so wide, however, that your audience wants to compare areas instead of lengths. Consider the following “Goldilocks” of bar charts: too thin, too thick, and just right.

From

Cover of Storytelling with Data: A Data Visualization Guide for Business Professionals

Note

bar width wider than white space always but not too wide