"Average" means that some are bigger, some are smaller. By definition, 50% of guys have a smaller than average penis.
But speaking as a guy with a smaller than average (but by no means tiny) penis I must say that all the media focus on "bigger is better", and the jokes about small penises, can easily give a guy an inferiority complex and damage his self-esteem. I have a fairly robust mental and emotional make-up, but even so, I cannot deny that I am sensitive about being seen fully naked - though not as sensitive now, as a mature adult, as I was when I was in my teens and twenties. I can walk bravely into an open gang shower, and have even stripped off on a nude beach, but my sense of vulnerability remains.
This is of course quite absurd, because being smaller than 50% (or maybe even 60%) of other guys in that part of my anatomy is no reflection on my masculinity, sexual prowess, intellect, character or anything else about me.
I'm not entirely sure why I found myself a member of a group which bills itself as a "large penis support group" and I have yet to discover what support most of these guys who boast about being "hung" either need or receive!!

But I am curious to get some honest comments from other guys, and of course the ladies who have found their way onto this site, about how you regard we guys who fall into the lower half of the scale.