Flowing Data Stories: The Art and Power of Sankey Chart Infographics

Sankey charts are a powerful, visual tool for depicting the flow of materials, energy, or people through a process. They are distinct in their ability to unravel complex systems, providing clear insights into the distribution of resources and the efficiency of systems at work. This article delves into the art and power behind the Sankey chart, exploring how they’re created and the many applications they serve in various industries.

The Story of Sankey Charts

Originating in the 19th century, Sankey diagrams derive their name from English engineer William Playfair, who is also credited with creating the first pie chart and bar chart. The term “Sankey diagram” was coined by Martin Sankey in a paper published in 1898, where he used such a chart to visualize the efficiency of coal-to-power plants.

Sankey charts are characterized by their two-dimensional, arrow-based layout. Flows are depicted by a set of arrows, where the thickness of each arrow represents the magnitude of the flow, while the arrow’s path indicates the flow’s direction and the processes or components to which it is assigned.

How to Create a Sankey Chart

Creating a Sankey chart involves several steps:

1. Identifying the Inputs and Outputs: Like all infographics, a Sankey chart begins with the identification of the primary components within a system (nodes) and how they connect (edges).

2. Quantifying Data: Accurately measure the volume, mass, or energy of each flow. This is essential for accurately conveying the magnitude of each flow.

3. Sketching a Frame: Using a canvas and rulers, sketch a grid or template that aligns with your data. This frame should be scalable to fit your required information.

4. Mapping Nodes and Edges: Position the nodes according to their importance and arrange the edges (arrows) to reflect the pathways of each flow.

5. Choosing the Flow Direction: Decide on a flow direction for each arrow. This often corresponds to the progression of the matter or energy through a system.

6. Determinate the Arrow Thickness: The key feature of a Sankey chart is the varying width of the arrows. Use software that can calculate and render these widths based on actual flow data to maintain accuracy.

7. Formatting and Finalizing: Ensure that all labels are clear and accessible. Adjust colors and styles to ensure the chart is both informative and visually engaging.

The Power of Sankey Charts

The art of Sankey chart creation lies in their ability to reveal insights that other charts cannot. Some ways in which Sankey charts demonstrate their power include:

1. Efficiency Analysis

Sankey charts are particularly useful for analyzing the efficiency of processes and systems. By highlighting losses and unnecessary by-products, they can inspire strategies for optimization.

2. Resource Distribution

They enable the detailed examination of resource consumption and distribution, which is crucial in fields such as environmental sustainability and economics.

3. System Performance

Sankey charts can uncover inefficiencies in the deployment of resources and highlight the bottlenecks that could otherwise go undetected.

4. Audience Friendliness

Because Sankey charts visualize complex flows, they help non-experts understand intricate processes that are typically challenging to convey through traditional data presentation methods.

5. Cross-Cutting Comparison

The chart design naturally allows for the side-by-side comparison of different systems or processes, making it an excellent tool for educational purposes and performance comparison.

Applications of Sankey Charts

Sankey diagrams are applied in a wide range of fields:

1. Energy Management

Illustrating the efficiency of energy conversion processes, from fuel to electricity or heat generation, is one of the most common uses of Sankey charts.

2. Environmental Studies

Sankey diagrams can depict the flow of emissions or pollutants, helping researchers and policymakers understand environmental impact and carbon footprints.

3. Business and Economics

In business, such infographics can demonstrate product flows, supply chains, and financial data. In economics, they are used to track the flow of capital or commodities.

4. Public Transport

They provide an excellent way to visualize the flow of passengers throughout the transport network, including bus routes or transit systems.

5. Education

Sankey charts are instrumental in illustrating concepts across various sciences and engineering courses, from thermodynamics to biology.

Conclusion

The art and power of Sankey charts are undeniable. With their unique ability to illustrate the distribution and flow of data, they continue to be an invaluable tool across numerous disciplines. Whether in industry, academia, or environmental management, the creation and use of Sankey charts bring clarity and sophistication to complex data visualization, making for a world better understood through flowing data stories.

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