It has no official significance, just a common term, and your link proves my point. I'm from Poland and by Larousse we're not central, by Brittanica we are.
For this survey it would be nice if we had a finer granularity. It would be interesting to see where the most HN users sit in Europe. Western, eastern and "other" Europe for a population of 700+ million people is rather sub optimal.
Compare that to the amount of options for the US with its 220 mio population.
Compare that to the amount of options for the US with its 220 mio population.
I'd propose a schema like this: http://commons.wikimedia.org/wiki/File:Europe_subregion_map_...