If one more person repeats that old saw about INFJs being the "rarest" of all the types, I'm going to throw myself on the floor and enjoy a good old-fashioned temper tantrum.
What is this famous old wives' tale based on?
Is it based on David Keirsey's estimation of the type distribution?
Okay, fine. So how scientific are those figures? Where is the research it's based on? (Because there isn't any. We know that for a fact. David made the percentages up.)
Okay, so maybe INFJ rarity is based on the statistics which are printed in the MBTI manual. That's reasonable. So where did they come from?
First, are we talking about the numbers Isabel Briggs-Myers estimated in 1957 based on the population of the school district where she conducted her studies?
Alright, so perhaps INFJ was the rarest type in that school. That doesn't mean by extension it's universally true everywhere.
So... perhaps rarity was determined after summarizing the figures according to that type survey they took. You know, the one in 1998 where telephone solicitors called various households throughout the country. They contacted 16,000 people and used the results of 3,009. (People were not given the opportunity to confirm their own best-fit preferences.)
Perhaps INFJs were the rarest of all the types for participating in such a survey? (I know I never participate in phone surveys.) So that's all that number reflects.
So if that study doesn't hold water... maybe we can rely on the statistics stored in CPP's computer that records all the MBTI scores. Hey, that's pretty solid evidence...
...until you concede that the instrument is only about 70% accurate, and the results which are stored have never been updated per anyone's validated type. (Thus, my INFP girlfriend who tested on the MBTI as INTJ will forever be listed in CPP's databanks as having INTJ preferences, despite the inaccuracy.)
So it's possible the MBTI has the most trouble identifying INFJs accurately. But that doesn't tell us how many INFJs there actually are.
Then... aren't there any valid studies out there?
Well, there are at least two sources (I have two right in front of me) that reflect different types as the smallest percentages of the population.
One comes from Portraits of Type: An MBTI Research Compendium, by Avril Thorne and Harrison Gough. It claims I_FPs have the smallest representation.
The other was printed in the Journal of Psychological Type, Vol. 37, 1996. The authors are Allen Hammer and Wayne Mitchell and their figures are based on a study that was concluded in 1992. In that study, ENFJs have the smallest representation.
So it seems not every study results in INFJ being the rarest type.
Of course you never hear about those studies -- you only hear that "INFJ is the rarest of all the types" (spoken in a prideful or dreamy tone).
And this story has been perpetuated to death!
The bottom line is, we don't have accurate statistics about type breakdowns for the earth's population (or even the U.S. population). Any statistics you might trot out have serious drawbacks associated with them, and are at best estimates -- sometimes guesses -- of what people think.
If "natural selection" were a valid theory, there should be 6.25% of each of the 16 types in the world -- an even distribution -- so that no one type is rarer than any other. But nobody knows for certain, since nobody has done an accurate personality type assessment of the entire population of the world, nor of a representative sample from all walks of life.
Why am I in a frothing tizzy over this? It's because this is frequently the ONLY thing people remember about the INFJ personality type! So it attracts people who are desperate to be RARE -- to be special -- to be unique-est of all. Then people crow about this "rare" label and don't want to give it up, whether or not the INFJ preferences really fit them. (Apparently it's a higher priority to be unique than it is to discover one's best-fit type pattern. Feeling special takes precedence over accurately matching the model.)
Agh! Agh! Agh!
Nobody knows how rare any type is, including the INFJ type.
If you rely on this particular statistic to ratchet yourself into believing you are unique and "special," I regret to say it's worthless. And frankly -- you don't need it anyway. You're unique and special regardless. All you require is giving yourself permission to believe it. And that, my friend, has nothing to do with statistics.