Less than half of people are stupider than the average
Why this asymmetry? High intelligence is reached when many factors coexist, whereas mental retardedness may be caused by only a single factor, such as a genetic error. So in the extremes of the distribution, additional intelligence and stupidity are caused by different random processes.
Back to the main point: we can analoguously clearly see that with the possible exception of Vatican, most of you earn or own far less than the average simply because the income and wealth statistics are very skewed in all countries except the Vatican.