[roel_v]

"but sorry, the "right" graphic to use here is the Mercator projection."

Maybe I'm just not understanding you, but this doesn't make sense to me. The site doesn't even show a map, what does the Mercator projection have to do with it?

[lifeisstillgood]

The data is number of people migrating from country X to country Y - so click on a country on the map of the world (Mercator Projection) and see lines appear linking UK with all the countries where people have emigrated.