50.9% according to the National sample figures in the MBTI Manual
Interesting!
"National" as in U.S.A., or by nation (Australia, Germany, France, Lichtenstein, Uzbekistan, etc.) I'm only half being a smart ass, because I actually do have a genuine interest in how that statistic might vary across various nations, especially those whose cultural values are significantly different than in Western societies.
For instance, in a fundamentalist Muslim nation, it does not behoove females to be too extroverted. Gaining energy from social interactions could very well get women in such nations a caning, beating or worse at the hands of the Muttawah, or their own husbands for the matter. So, does such fear of punishment predispose women in fundamentalist Musilm societies to "become" more introverted for the sake of self preservation?
On the flip side, are American women more prone to "become" extroverted in order to pursue the many potential gains available to individuals willing to put themselves out in all kinds of situations in order to find opportunities/wealth/a suitable mate?
The answer to these questions seems to hold part of the answer as to how powerful GENOTYPE is Vs. ENVIRONMENT. (That is assuming that one's MBTI type is genetically inherited in some significant capacity. Come to think of it, is it? Has anyone ever prone that?)
-Halla