Mapping cooperation between countries in OSM

Hi,

For a long time I have wanted to know where people from a given
country also contribute in OpenStreetMap.
I have analyzed all the nodes in the OSM Planet from the 15th June
2013 and I came up with this map :
http://fredericbonifas.github.io/OSM-cooperation/

One identified bias is that each contributor is assigned the country
where he has contributed the most as his main country. But this may be
false.

Best