Stat's are taken from git repo. In general, it's not trivial to recognize the same person if he/she uses different names/emails. There isn't any heuristics in place and some people can appear more than once.
23 karma · joined March 5, 2015
"England officially became the second most crowded major country in the EU in 2008, according to figures released by the British Office for National Statistics"
I believe, it's because people from continental Europe sometimes don't differ between UK and England - but it's sensitive issue in the UK :-). UK is actually the first if we take European countries with over 20M people - 255people/km2.