A donut chart is also area<->arc length proportional. Intuition: a donut chart is what remains of a pie chart when a smaller version of the same pie chart is re

A donut chart is also area<->arc length proportional. Intuition: a donut chart is what remains of a pie chart when a smaller version of the same pie chart is removed from the center. If the two pie charts are proportionally correct, their difference must be proportionally correct.