As I mentioned previously, and judging from the graphs, the standard deviations of the IQs are obviously mixed up, because they were not determined in the questionnaire, and probably people who answered are not educated about them either. Including IQs in s.d. 24 with those in s.d. 16 and 15 is bound to inflate the average IQ. The top scores in that graph, or at the very least some of them, are in s.d. 24, which means that they would be a lot lower in s.d. 15. IQ 132 is the cutoff for s.d. 16, while s.d. 15 is the one most adopted in recent scientific literature. For s.d. 24, it is 148. Mensa and often people on the press like to use s.d. 24 to sound more impressive to amateurs.

This probably makes tests like the SAT more reliable as an estimation, because they have the same standard for all who submitted their scores, although in this case the ceiling effect would become apparent, because perfect or nearly-perfect scores wouldn't go upwards of a certain IQ.