To play in a World Cup national soccer team, a player must be a citizen of that country. But most World Cup players don't regularly play in the nation of their World Cup team. Some hold dual citizenship; others simply play for a league team in a foreign country where citizenship rules don't apply.
In this elegant chart, Guy Abel, a statistician and R programmer at the Vienna Institute of Demography, illustrates how the World Cup national teams are drawn from League players from around the world. (Click to enlarge.)
The arrows on the chart flow FROM the World Cup national teams TO the countries where the players currently play in league teams. Most of the players in Australia's World Cup team, for example, actually play for teams in the USA, South Korea, and European league teams. By contrast, about a third of Italy's team and almost all of Russia's play for domestic leagues (note the arrows folding back on themselves indicating players who play in home leagues).
The chart was created in the R language using the ciclize package. The underlying data was scraped from Wikipedia, and the code to create this plot is available on github. Guy gives other several examples (with R code) of creating such "circular migration flow plots" on his blog.
Guy Abel: 2014 World Cup Squads