From Origin to Application: Understanding Sankey Charts in Power BI 

A Sankey chart helps visualize the flow of data between different stages. It shows how values move from one category to another using nodes and flows. The nodes represent stages, and the flows represent the magnitude of movement between those stages.  

Using a Sankey chart in Power BI, you can simplify complex pathways, such as tracking website traffic, energy consumption, or financial transactions. It brings clarity to large datasets by highlighting dominant flows and bottlenecks. 

In this blog post, we will learn about Sankey, its origin, different types of Sankey, and what are the real life applications of this visual.  

Table of Contents 

1. What is a Sankey Chart? 

2. A Glimpse into History: The Origin Story 

3. Sankey Diagram vs. Alluvial Diagram 

4. Different Types of Sankey Charts 

5. Sankey in Action: Real-World Use Cases 

1.What is a Sankey Chart? 

In a Sankey chart, the width of each flow (arrow) is directly proportional to the quantity it represents. This makes it easy to see which paths are the most significant. The chart usually shows a flow starting from a source, passing through intermediate stages, and ending at a target. 

One unique feature of a Sankey diagram is the conservation of flow. That means the total input into a node equals the total output. This helps highlight dominant pathways, bottlenecks, and important areas in the data flow. 

If you want to present a complex process in a simple, visual format, then a Power BI Sankey diagram is a great option. 

2. A Glimpse into History: The Origin Story 

The Sankey chart isn't a modern invention. Its origins can be traced back to Charles Minard, a French civil engineer renowned for his innovative statistical graphics. While not explicitly called a "Sankey chart" at the time, Minard's graphic depicting Napoleon's disastrous Russian campaign of 1812 is widely considered the precursor. This masterpiece visually represented the size of the army at different points during the campaign, along with temperature and distance, painting a stark picture of the devastating losses. 

Source - Wikipedia

However, the formal naming of the chart came later, attributed to Captain Matthew Henry Phineas Riall Sankey, an Irish engineer. In 1898, Captain Sankey used a similar flow diagram to illustrate the energy efficiency of a steam engine in The Proceedings of the Institution of Civil Engineers. His clear and effective visualization of energy input, losses, and useful output cemented this type of diagram in the visual lexicon, and thus, the "Sankey chart" was born. 

Source - Wikipedia

3. Sankey Diagram vs. Alluvial Diagram 

The terms Sankey diagram and Alluvial diagram are often used interchangeably in data visualization. However, while they share similar properties, there's a core difference between them. 

A Sankey diagram primarily focuses on quantified flow within a system or process. In contrast, an Alluvial diagram highlights multiple categories and their relationships across various stages. 

Here's a simplified way to think about it: 

• Sankey: "How much of X went from A to B?" (Focus on quantitative flow) 

• Alluvial: "How did the composition of this group change from Stage 1 to Stage 2?" (Focus on categorical shifts and re-grouping) 

With Inforiver Analytics+, you can create both Sankey and Alluvial diagrams in Power BI. 

Now that you know the difference between Sankey and Alluvial, let’s understand the different types of Sankey. 

4. Different Types of Sankey Charts 

While the fundamental principle remains the same, Sankey charts can be adapted to suit various data structures and analytical needs. Here are a few common variations: 

• Simple Sankey Chart: This is the most basic form, showing a single flow path with clear sources, intermediate nodes, and sinks. 

• Multi-Level Sankey Chart: These charts incorporate more than one level of intermediate nodes, allowing for a more granular view of the flow through complex systems. For example, in website analytics, you might track traffic sources, then the pages visited, and finally the conversion points. 

• Circular Sankey Chart: Instead of a linear flow, circular Sankey’s can visualize cyclical processes or relationships where the end point feeds back into the beginning. This is often used for representing energy cycles or material flows. 

• Network Sankey Chart: These charts can depict more intricate networks with multiple connections between nodes, not necessarily following a strict linear progression. They are useful for visualizing complex relationships in social networks or supply chains. 

The choice of which type to use depends entirely on the data you're working with and the insights you want to extract. 

5. Sankey in Action: Real-World Use Cases 

The versatility of Sankey charts makes them invaluable across a wide range of industries and applications: 

• Energy Management: In energy production and industrial processes, Sankey can be used to track energy consumption and losses. It helps in identifying areas for efficiency improvements. Here is an example of hydrogen efficiency. 

• Financial Analysis: Sankey helps in visualizing the flow of money in income statements by highlighting the income and expenses. Apple's income statement is one of the popular Sankey examples that float around on the internet. It captures all the different revenue streams that contribute to revenue and then the flow towards net profit after deducting all the expenses and taxes. 

• Website Analytics: Tracking user journeys, understanding traffic flow from different sources to various pages and conversion points. This is a Power BI Sankey diagram created using Inforiver Analytics+ visual. 

• Job Application: Another popular example seen in Sankey is tracking the flow for candidate hiring. Sankey can help visualize the drop-off rate at each stage of the interview towards the last step. 

• Environmental Studies: Tracking the flow of resources, pollutants, or the impact of human activities on ecosystems. 

Source: Research Gate

• Manufacturing: Analyzing material flow in production processes to identify waste and optimize resource utilization. 

Source - Energy.gov 

In each of these scenarios, the Sankey chart provides a clear and intuitive way to understand complex flows and identify key areas for attention or improvement. The visual emphasis on the magnitude of each flow makes it easy to spot the most significant contributors or detractors within a system. 

Conclusion 

A Power BI Sankey diagram is more than just a pretty visual—it's a powerful tool to uncover insights from complex processes. Whether you're analyzing marketing funnels, product flows, or financial breakdowns, a Sankey chart in Power BI offers a clear view into what matters most. 

Looking to create a multi-level Sankey chart in Power BI? Tools like Inforiver Analytics+ make it easy with intuitive formatting and interactive features. 

Start building your own Power BI Sankey visuals today to make your reports more insightful and engaging. Start your free trial today.