One row of a dumbbell chart: a category and the pair of values compared at
it.
The pair is what the chart is for -- before and after, two groups, two
years -- and the segment drawn between the dots is the comparison. Which of
the two is larger is not fixed: a dumbbell showing a decline draws end
below start, and a chart usually contains both directions at once.
The change between them is deliberately absent, and derived instead. A
drawn segment cannot disagree with the dots it joins, so an authored delta
is a second source of truth for a quantity that already has one -- and the
one a reader would be told is the one the chart did not draw.
One row of a dumbbell chart: a category and the pair of values compared at it.
The pair is what the chart is for -- before and after, two groups, two years -- and the segment drawn between the dots is the comparison. Which of the two is larger is not fixed: a dumbbell showing a decline draws
endbelowstart, and a chart usually contains both directions at once.The change between them is deliberately absent, and derived instead. A drawn segment cannot disagree with the dots it joins, so an authored delta is a second source of truth for a quantity that already has one -- and the one a reader would be told is the one the chart did not draw.