Each group shows three bars per region: requested, received, and actual expenditure. Bars start at zero. Click legend items to isolate a series. Hover any group for detail. Values in USD millions, FY 2024 (simulated).
A multi-set bar chart places multiple bars side-by-side within each category group. The viewer simultaneously reads two things: the length of individual bars (how large each series value is for that category) and the relative lengths of bars within the same group (how the series compare against each other at that category). The primary perceptual channel is length along a common baseline — the most accurate quantitative judgment available to the human visual system, according to Cleveland and McGill's hierarchy of perceptual tasks.
The structural signature is the nested scale: one scale governs the position of each group along the x-axis; a second, inner scale governs the position of each bar within its group. In D3, this is implemented as d3.scaleBand() nested inside another d3.scaleBand() — the outer band sets group widths, the inner band subdivides each group into individual series bars.
The data has a specific two-level comparison structure: the analyst needs to compare values across regions (is the Middle East gap larger than East Africa's?) and within regions (how does received compare to requested in the same region?). A multi-set bar chart handles both questions simultaneously. The within-group comparison is immediate — adjacent bars share a baseline and differ only in length. The across-group comparison is also readable because the same series appears in the same position in every group, so the eye tracks a single color band across all five groups.
The funding pipeline story has a natural left-to-right series order: Requested → Received → Expenditure follows the logical flow of money. Placing the series in this order inside each group encodes a mini-narrative — the viewer reads left to right and sees each step of the pipeline contracting. This ordering decision is carrying analytical weight, not just aesthetic preference.
A stacked bar chart would allow the total of all three series per region to be read directly — but the funding requested, received, and expenditure values do not sum to a meaningful whole. Stacking three pipeline stages would imply they are additive components of a total, which they are not. More critically, the within-group comparison between series would be degraded: only the bottom series has a common baseline; all others float and require the eye to judge floating bar lengths, which is less accurate than common-baseline judgment.
A small multiples line chart (one panel per region) would make the within-region trend across series easy to read but would make cross-region comparison of the same series harder — the eye has to jump between panels rather than tracking a single color. For five regions with three series, small multiples adds panels without adding information.
A dot plot would reduce the visual weight and show the same data more cleanly for audiences who resist bar charts — but dot plots sacrifice the strong visual encoding of area (bar height × width) that makes the magnitude difference between Middle East ($6.15B requested) and Latin America ($1.92B requested) immediately apparent.
The FT Visual Vocabulary places grouped bar charts in its Comparison category alongside simple bar charts and dot plots. Its note: use a grouped bar chart when the subcategory comparison within groups is as important as the comparison between groups. The test — if you only need to compare totals across categories, a simple bar chart suffices. If you need to see the internal breakdown, group or stack. If the components are not additive, group rather than stack.
The expenditure bars carry a diagonal hatch pattern in addition to their dim-gray fill. This provides a redundant visual encoding that does not depend on color: a viewer with deuteranopia or protanopia who cannot reliably distinguish the three series colors can still identify expenditure bars by their texture. This is the WCAG 2.1 principle that color must never be the sole differentiator — shape, pattern, or position must carry the same information. The hatch was chosen (rather than a solid pattern) because it preserves the perceived bar height, which is the primary encoding channel. A solid tonal difference would change the perceived brightness and distort the length comparison.