Challenge 2: Rebuilding an Unreliable Pie Chart as a Bar Chart — Solution Walkthrough

Why the pie chart makes this task difficult:

With 9 categories, several of them close in size, the colleague is
being asked to compare SLICE ANGLES (and the areas those angles
sweep out) to determine which is genuinely larger. The human eye is
measurably unreliable at this specific kind of comparison — angle and
area differences that are mathematically real (say, a 2-3 percentage-
point gap between two categories) are often too subtle to perceive
correctly just by looking at two wedge shapes side by side, especially
once there are enough slices that they're no longer positioned
conveniently next to each other around the circle.

Recommended rebuild: a Bar chart (horizontal bars work especially
well with 9 category labels, since they stay readable without
rotating any text).

Why a bar chart answers the question more reliably:

A bar chart converts the same comparison into LENGTH along a shared,
common baseline — and length is the one visual property people are
demonstrably good at comparing precisely. Once every category's
expense is drawn as a bar starting from the same zero point, the
question "which of these two close values is actually bigger" becomes
a matter of directly comparing how far two bars extend, rather than
mentally estimating and comparing two wedge angles or areas that
aren't lined up against any shared reference line at all.

Notes:
- Sorting the bars from largest to smallest (rather than leaving them
  in whatever order the original categories happened to be listed)
  makes the comparison even faster to read, since the reader doesn't
  have to hunt across the chart to find the largest bar.
- This is the direct, concrete case this chapter's own tip box points
  toward: whenever a pie chart's real job is precise comparison rather
  than a simple few-category composition snapshot, a bar chart is the
  more honest and more readable choice.