Food Security Anchors 47 percent of All Funding , Shelter Surged in Mid-2022 Then Normalised as Ukraine Emergency Peaked Figure 66.1 , Food Security Anchors 47 percent of All Funding

A stacked area chart renders multiple time series as filled regions stacked vertically. Each series begins where the previous one ends , not at zero. The result is that the total height of all layers at any point in time equals the sum of all series values. The viewer simultaneously reads two quantities: the total (the height of the uppermost boundary) and the composition (the relative thickness of each layer). This dual encoding is the defining capability of the stacked area form.

The message has two simultaneous parts: total humanitarian funding grew from ~$880M/month to a peak of ~$1.14B/month, and within that growing total, the composition shifted , Shelter and NFI surged sharply in mid-2022 (Ukraine emergency) then contracted, while WASH grew modestly and steadily, and Food Security maintained its dominant share throughout. A line chart can show either the total trend or individual sector trends, but not both simultaneously at the same scale. A bar chart can show composition at individual months but loses the continuous flow.

Only the bottom series (Food Security) has a common baseline of zero. Every other series floats , its bottom edge is not zero but the accumulated total of all layers below it. This means precise comparison of an upper series across time requires the viewer to estimate two values (the y position of the floor and ceiling) and subtract them, which is less accurate than reading a single position on a common scale.

A stream graph (the same chart with d3.stackOffsetWiggle ) would center the stack on a baseline that shifts over time, creating an organic, flowing shape. Stream graphs reduce the visual dominance of large series at the cost of making it impossible to read any absolute values or the total. They are optimised for pattern and shape recognition, not for reading specific quantities. For a funding dataset where the total and individual sector values need to be communicated, a stream graph would be the wrong choice.

framework , FT Visual Vocabulary The FT Visual Vocabulary places stacked area charts at the intersection of Change Over Time and Part-to-Whole . Its decision rule: use a stacked area when the total is meaningful and you want both total trend and composition over time. Use a line chart when precise individual series comparison is the priority and the total is secondary. Use a stream graph when pattern and aesthetic flow matter more than readable quantities.

Paste this into Claude Code to generate a working version of this chart, plus its data file. The result will not be a perfect replica , the goal is that the reader can run the prompt, get a chart of this type, and read its source. Generate a complete, self-contained stacked area in D3 v7. Two files:

The ideas in this chapter didn't appear from nowhere. Émile Levasseur was a 19th-century French economic geographer who produced some of the first stacked-area charts of national production and trade , building the form that would later become the streamgraph and the modern stacked area chart. Émile Levasseur, circa 1880. AI-generated portrait based on a public domain photograph (Wikimedia Commons).

Only the bottom series (Food Security) has a common baseline of zero. Every other series floats , its bottom edge is not zero but the accumulated total of all layers below it. This means precise comparison of an upper series across time requires the viewer to estimate two values (the y position of the floor and ceiling) and subtract them, which is less accurate than reading a single position on a common scale.