Nine Slices, a Truncated Axis, and a 'Best' Region
An analytics team is preparing a quarterly review for nine sales regions. A colleague proposes a 3D pie chart with nine slices to show each region's share of total revenue, and a second line chart with the y-axis starting at 80% of revenue to make the growth trend 'look clearer.' They also want to call out Region 4 as 'best' because it has the highest absolute revenue, although Region 7 has the fastest growth from a smaller base. Region 4 is 22% of total revenue but its growth is flat; Region 7 grew 31% year over year but is 6% of total. The audience is regional managers who will use the deck to make staffing requests. You have 15 minutes before the deck is locked, and the colleague is senior to you. The underlying table has revenue, prior-year revenue, and headcount by region for eight quarters.
1. Critique the two proposed charts and the 'best region' framing. Be specific about what each choice would make a manager conclude.
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The nine-slice 3D pie chart fails on both perception and precision: people cannot reliably compare nine angles, 3D perspective distorts the slices, and the chart does not support the staffing question, which is about size and change. The truncated-axis line chart exaggerates small movements: starting at 80% makes a modest change look dramatic, so a manager may infer a crisis or a boom that is not in the data. Calling Region 4 'best' conflates absolute size with performance: Region 4 is 22% of revenue but flat, while Region 7 is only 6% but growing 31%. A manager could staff Region 4 as a reward and under-resource the region with the clearest growth signal. The framing is not just stylistic; it changes the decision.
2. Recommend alternative chart types and encodings for revenue share and growth, and say what you would put on each axis.
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For revenue share, use a sorted horizontal bar chart with regions on the y-axis and revenue or share of total on the x-axis, starting at zero and labeling totals. Sorting makes ranking easy and avoids the angle-comparison problem. For growth, use a line chart by quarter with a zero baseline if plotting revenue, or plot year-over-year percentage growth directly with a zero line; do not truncate the axis. If the goal is to compare prior year to current year, a slope or dumbbell chart with prior-year and current-year revenue on a common zero-based axis is clearer. Use one accent color to highlight Region 4 and Region 7, not nine competing colors. Each chart should answer one question: who is large, and who is changing.
3. Draft a two-sentence narrative that avoids the misleading framing while preserving the useful signal for staffing.
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'Region 4 contributes the largest share of revenue at 22% but has flat growth, so its staffing case is about protecting current volume. Region 7 is only 6% of revenue but grew 31% year over year, so it may need capacity if that trend continues.' This keeps both facts visible, avoids calling either region simply 'best,' and gives managers a concrete decision frame: protect the large base versus invest in the fast-growing base. If the deck must highlight one region, highlight the tradeoff rather than a single winner.