Today I was wondering how smart I was compared to other INTJs. I had already taken an IQ test a little while back, so I thought I would just google average INTJ IQ. I tried entering a variety of queries, and it seems that this information does not exist.
You CAN find lots of information about frequency of high IQ but, the frequency of high IQ does not actually tell you what the mean IQ for the different types is, or the standard deviation.
INTPs are the smartest according to a chart I found with 3.52% being geniuses, as opposed to 2% in the general population.
Note that this makes the relative frequency of INTP geniuses equal to 1.77. Some mathematically ignorant people online seem to think this means that there are more INTP geniuses than non-geniuses, so that INTPs have something like a 63.9% chance of being geniuses, which is absurd. There is a lot of ignorant blogs which you have to disregard.
I did some quick math with Gauss functions, and calculated that if the distribution is the same, the average INTP IQ only has to be 105 (assuming 100 average and 15 standard deviation) in order to get the ratio of geniuses given here. That would be a rather trivial advantage. A small change in mean can make a big difference in relative number at the fringes.
Doing the same math for the ESFJ, which has the smallest percentage of geniuses, produces an average IQ of 77. That is not so trivial.
It doesn't seem right that the dumbest personality type has borderline mental functioning and the smartest has barely above average IQ. It would take more rigorous calculations that I can't be bothered with to prove it, but this seems to put the average at less than 100. Upon thinking this over a little bit, I suspect this may indicate that different personality types have tighter distributions than the general population. If a subgroup has a smaller standard deviation than the population as a whole, then their representation in the fringes would be less than it would be with a broader distribution. So, if you assume that personality types have smaller standard deviations than the general population, then both the average ESFJ and the average INTP would be smarter than my calculations assuming the same standard deviations would indicate.
So the population may be 16 overlapping bell curves with relatively tight groupings, but different means, which appears to be one big broad bell curve for the whole population.
BTW, my opinion on IQ is that is measures analytical intelligence, which is not the only thing that your brain does. For instance, a skilled musician or sportsman is obviously using his brain to do the complicated things that he does, but these skills do not translate to the IQ test. I would be inclined to think that total brain functionality is broader than measured IQ and probably doesn't change a great deal between the different personality types, or else you'd expect measurable differences in brain weight, size, & shape of people with different personalities, which so far as I know, is not the case.