In a recent post I discussed the use of heat maps to display patterns of data that are often shown in a tabular format ( US 2018 grape harvest prices visualised ). In the current post I will discuss an alternative type of graph, one that shows flows of things from on place to another — the Sankey diagram. This has obvious relevance to the wine industry, in which grapes and wines move globally as well as nationally.In this case I will look at the movement of bulk wine between countries. I have compared world-wide imports and exports in an earlier post ( Where does all of this wine come from and go to? ), but not shown the actual flows of the volumes.The data come from Comtrade , the United Nations International Trade Statistics Database. I accessed the data available for 2017 in the category: "Wine; still, in containers holding more than 2 litres" (code 22042). This may include pretty much anything (bulk or otherwise), except import/export of single bottles of wine, but excludes sparkling or fortified wines.For an example of a Sankey diagram, let's look at Spain, the world's largest bulk-wine exporter. Spain actually exported to 116 countries in 2017, according to the database, but I have shown only the top 15 countries in the figure.The diagram shows flows from left to right, so in this case the exporting country is on the left and the importing countries on the right. There is one line connecting to each importer, with the thickness of the line indicating the relative volume of wine. So, in this case France is far and away the biggest importer of bulk Spanish wine, followed by Germany. The countries tail off pretty quickly, past Italy and Portugal.That France is a massive importer of bulk wine has been commented upon before, and it is usually assumed that it is being added to cheap French wine, without being mentioned on the label (the latter is only required if the addition exceeds a certain percentage). In this case, though, the Comrade database show that the reported Spanish exports exceed the reported French imports by 4 million litres, which is rather a large discrepancy (0.9%).As an alternative, we can look at Germany, which is the world's largest bulk-wine importer. Germany actually imported from 28 countries in 2017, but once again I have shown only the top 15 countries in the figure.The diagram shows us that, at the moment, Italy slightly exceeds Spain as the main source of bulk wine for Germany, with a pretty rapid decline after that.We can also look at both exportsimports. For this, we might look at the USA. In 2017, the USA exported to 58 countries but imported from only 15 countries, when looking at large containers. These are shown in the next two graphs.Clearly, the United Kingdom is far and away the largest recipient of American bulk wine, while Chile, New Zealand and Australia vie to be suppliers.The Sankey diagram also allows us to combine imports and exports into the same graph. The data for the next figure are taken from the American Association of Wine Economists' Facebook page: World's Top 30 Bulk Wine Routes 2017 . So, the Sankey diagram illustrates the 30 largest movements of bulk wine during 2017. As above, wine is exported from the left of each line and imported at the right, so that importer / exporters will lie in the middle.In this case, the diagram indicates that Spain exports to Italy, which in turn exports to France, which exports to Germany. Spain also exports directly to France and Germany, and Italy also exports direct to Germany. Any flow of bulk wine opposite to these flows is not among the top 30 routes. Note that it would be impossible to show all of the routes in a single diagram using this arrangement, because flows can only go from left to right.Perhaps the most interesting outcome of this arrangement of the diagram is what is shown about Canada, which exports more bulk wine to the USA than it produces! Clearly, Canada is re-exporting wine, mainly imported from Australia, while there is also a direct route from Australia to the USA.Another version of this same diagram is actually shown in the comments section of the AAWE page linked above, created by Yuta Kanazawa. I have included it here, because it is such a pain to directly access old Facebook posts. In this case, countries appear atthe left and right of the diagram, depending on their role as either an exporter or an importer (eg. Canada, France, Italy, USA). With this arrangement, rather than the one above, we could, indeed, show everything.