Flow maps show branches of data which form part of a whole and are often used to show derivative products made from a single source. These were quite popular in the early 20th Century to show shipping traffic from ports. In this example it shows the components that contribute to the 3M stock price. Post-its and office produces are 12% of the stock price, while Industrial Adesies and medical supplies are much larger.
In this interactive graphic from Trefis it asl shows market size and share (on the right).
Sankey Maker (includes a Sankey blog).