People, please don't forget me!!!
I mean, I had posted the compilation of the official MBTI population counting per country on the wiki here:
Link
It would be a good idea to make this thread sticky
"MBTI population by country" instead of this one
"Approximate MBTI percentages of MBTI per population",
@Wyote .
I also do not have a whole theory why INFJs are rare (I do for ENFJs), but I have a partial explanation to that.
It happens that Intuition and Perceiving are correlated - or Sensing and Judgment are correlated, even inside the official MBTI, also on Sakinorva test, and although the keys2cognition one seems to be free from it, xNxJs are less intuitives than xNxPs in average.
These above are the correlations for US country, but other countries, even Japan, follows a similar pattern. In facet terms, all facets have the correlations as well. Explaining it conceptually is a little bit hard but far from impossible, there are N stuff that partially points to Perceiving (more than Perceiving stuff pointing to intuition in my opinion).
So, since there are these tendencies, it is very unlikely for any XNXJ or XSXP type to be the most common type in any country, and this can explain until some point - not entirely - why INFJs are rarer. ENFJs being rare can be explained entirely by this because "it gets further".