The optimal number of categories depends on what we want to show:
- For display of common trends: in this case, the number of categories can be bigger (up to 50 bars);
- For display of comparison within categories: in this case is better to reduce the number of categories (up to 12 categories).
The 'Visually’ website suggests that we should, in any case, when we are comparing within categories, set the limit under 12 categories - the lower the number of categories - the better. When displaying trends, we can increase the number of categories up to 50 bars, if this helps us demonstrates certain trend better.