The stream graph is a range spline area chart in which the points have been moved up or down, in a proportional manner, to expose a symmetrical view based on the middle horizontal baseline. Stream graphs were introduced in 2008 in a New York Times article on movie box office revenues.
Our Sales Differences multi-series demo charts show two filled-in symmetrical zones, centered on one side and the other of the horizontal middle baseline, each between a pair of smooth lines with product quantities sold in 17 consecutive years, from 2000 to 2016. These are multi-series charts, with first series the sales difference between US and France, and second series the sales difference between France and UK.
Also check this animated demo: