Using a Sankey diagram to map a supply chain

Supply chains are natural Sankeys: material enters from suppliers, moves through facilities, and leaves through channels, losing some volume to waste and returns along the way. The difficulty is scale — a real supply chain has hundreds of nodes and a chart cannot.

Group ruthlessly on the left

Nobody needs 140 supplier nodes. Group by tier, by region or by material, and keep the top three or four named individually if concentration risk is the story.

Keep the middle physical

The centre column works best as places: plants, warehouses, distribution centres. That is what makes the chart actionable, because bottlenecks live in places rather than in abstractions.

Draw the leakage

Waste, spoilage, returns and shrinkage should each be a visible ribbon. A supply chain Sankey that ends with everything neatly arriving at customers tells you nothing you did not already hope was true.

Volume or value, never both

Units and euros produce different charts, and both are useful. Draw two diagrams rather than one chart with mixed widths, and name the unit in the title.

• Suppliers grouped by tier or region.
• Facilities as the middle column.
• Waste, returns and shrinkage as explicit destinations.
• One unit per chart, named in the title.

The version that gets used in meetings is almost always the simplified one. Build the detailed chart for yourself, then publish the grouped version.