I definitely can't fathom 75% of the world being 6s. It's certainly not in the US and certainly not in the locality where I live. Like Paradigm, I can agree that there are more 3/6/9s, but not by large orders of magnitude. Personality type statistics are highly questionable, anyway... there are so many validity problems and ultimately I don't believe it's really possible to get an accurate empirical read. Regardless, 75% doesn't make sense either in external observation or internal logic.
Anyway - I really like 4s as friends, though I don't think we would tend to make good relationship partners.
I love 4 aesthetic awareness, candor, individuality, willingness to buck the status quo, expressiveness, longing for ideals, future orientation, creativity, and the serious dedication that they bring to their labors/art/work. I met back up with an old 4 friend (I suspect 4w5?) recently, and we have really hit it off. We both treasure knowledge and reflectiveness, and have had challenging experiences in the social realm. I think we have both found a comfortable person with whom to share our painful social experiences, because we are not judgmental of the other for being different - if anything, it is so interesting to find someone who has willingly (but not without some reluctance/despair) departed from the norm. We both understand each others' frustrations about imperfection and external pressure in our jobs - supervisors who are pushy and irrational, being asked to deviate completely from the original intent of our projects, being forced to move at a pace too fast for us to produce quality work, and so on. I think we have both found another person who is into encouraging our need to make art that really speaks out from our souls, and that is a rare, beautiful thing. We also seem to have zero problems with both of us going weeks with only texting each other and not meeting up in person because we are just going home and avoiding spending a lot of energy. Haha!
That said, I have a hard time with 4's disdain for the ordinary - while I love the drive for the extraordinary, I also I feel strongly that everyone and everything should be valued in its own right and elitism makes me feel very conflicted - so while I often agree on some level, and can laugh and appreciate it, it is hard for me to stay for very long on that same page. Relatedly, it is hard for me not to hear 4s as being disdainful of others when they are making comparisons, which I then have to continually reconcile with the understanding that 4s themselves often feel inferior to others. This can be an emotionally exhausting dance. Ironically, being an artistic, reflective, sensitive INFP, sometimes I feel like 4s don't leave me room to celebrate and enjoy myself... as if, if there is any overlap or similarity between us, we cannot celebrate together - rather, those aspects are already "taken", and I have to find some way to differentiate myself clearly from them first in each area before they will acknowledge me. Finally - I desire a lot of positivity and stability out of a partner, since it helps me orient, enjoy, and move forward in life. I think it would be an unfair demand on a 4, most of whom don't seem to naturally produce these elements, for me to constantly be seeking it from them.
So - even though I treasure 4 authenticity and depth, and delight in their aesthetics, I think we make better friends who can enjoy one another and then take a break, rather than romantic partners, who need to be constantly collaborating and supporting one another through life's ups and downs. But, of course, everyone is different! Just off the top of my head I could easily see successful pairings of 4w5+6w5, or 4w3+6w7... they certainly share some similarities in outlook. For some 4 and 6 may be the perfect partnership.