Displaying gaps

Comparing gaps means displaying the distance between (usually) two categories or between categories and a reference value. Examples:

  • Wage gaps between men and women;
  • Distance between a category and a reference value (regional value compared to the national average)

This is similar to analyzing order and ranking, but our focus is less on the absolute value and more on the gap. Like order and ranking, a key issue with these charts is how to order categories:

  • The alphabetical order of categories is rarely the right solution, and should you should avoid it.
  • Preserve the implicit sequence in ordinal variables, like names of months or weeks.
  • When there is no order (like country names), order categories by the quantitative value or gap value.

It should be clear for the reader when position is reversed (increase vs. decrease, category A is higher or lower than category B). Color and/or arrows are commonly used to signal this.

Common geometries

A bar (vertical or horizontal) is the most common geometry when comparing gaps.