Curious. This question sparked my mind this morning and although I get the feeling it is simple enough to be deemed self-explanatory (by Ni), I still feel like asking everyone their thoughts. Statistics keep showing up that INFJs are the least amount inhabiting the types of personalities in the (known, tested) world, with INTJs a close runner-up. I have seen ENTJs sometimes listed as second bumping INTJ third but for the sake of keeping to my original question, let's just assume specifically INTJs and INFJs are whom we are discussing in this thread.
My assumption to this is that INTJs have an auxiliary Te which is more "understandable" if not "accepted" by society, if you even dare to conjunct it with Ni dom. Even if INTJs are considered the silent, independent, hustling (lol hustling) outsiders of society who deviate from the norm, they are still to some degree, "acceptable" because they can at least direct with that Te and make some great changes or accomplishments if not just get everything done better and more efficiently than say sensors who naturally ride over the population and keep to whatever's been done already, by, doing what's been done already which provides a restraint or firmer grounding (not saying anything inherently bad about sensors, but maybe I am referencing Si mostly). For this aspect INTJs are often praiseworthy, respected and admirable as much as they are seen for how offbeat they are, and even still they are closer to society and the "real world" than I think an INFJ typically is.
Not only that overall preference for Te but also, with tertiary Fi in the wings they are able to more subjectively relate (or disassociate) from individual feelings and values. They literally still have their own set, person... or identity intact as opposed to the INFJ who is pretty much the manifestation of Pisces, floating in the endless eternal ocean feeling and connecting with everything to which they don't really understand themselves for lack of firm grip on their own, personal, values. It's the dissolving of the personal ego, in a way, which I think INTJs still have their own individuated ego enough to see readily their own boundaries, goals, etc to still function like a regular human being on earth (I use the term "regular" loosely). INFJs have values, but through Fe, and Fe is governed by Ni dom, which is trying to synthesize and encompass... practically everything vague and unknown or unseen, from my understanding (and look at that tertiary Ti trying to make sense and rearrange all their connections in a logical format-- they can make any hunch have rational pertinence by means of picking and choosing).
Going back to the Te comment and how it is more widely understandable and accepted by majority of the world, I'm not saying that I believe there are more INTJs than INFJs because INTJs have been trying to be more accepted by the world, as that isn't the case clearly. They function completely as their own and differently yet utilize that understanding as a guiding tool. The world as we know it did not breed INTJs and INFJs, and yet they came in their numbers as such (as with all the other types, relatively)... and just because something isn't widely acceptable, doesn't mean it doesn't exist or have a purpose... so why?
I'm not trying to differentiate INFJs and INTJs as much as I'm trying to gather insight on why INFJs would be, supposedly more "rare" than INTJs, though I get I'm answering my own question. LOL But the reason I wonder is because part of me doesn't actually think INFJs are that rare. It might take me a bit longer to explain why I think that, or I simply just don't know yet atm.
In the meantime, I want to hear your guesses or insights to it. In your opinion, why would INFJ be the least amount of the population instead of INTJs. What would it look like then if INTJs were the 1% of the population instead? Why is it laid out, or has been founded to be, that way?