When we started writing our Ebook (available here), we discovered there were very few reliable studies. First of all, we had to reject many public and private studies. There were many studies where the measurement methodology has not been published. Without clear measurement procedure, you can’t compare the measurements to anything. Then, we had to reject all self reported studies, like the Kinsey institute penis size study. Self reported studies are not reliable at all since everybody can cheat on their penis size and many mistakes can be done. Only measurements performed by a medical staff is valid. Then, we had to reject all studies that measured the flaccid and stretched penis size. Actually it has been found there is no link between flaccid, stretched and erect penis size. You cannot forecast a man erect penis size from a stretched or a flaccid penis size. In other words, studies that measured flaccid or stretched penis sizes are totally useless to us. We ended up with less than 5 studies where we found the erect penis sizes measurement procedure. Unfortunately, even with valid penis size studies it is difficult to compare it from one to each other. For instance, one study will use drug injection for artificial erection and another will not. It would be good to have a standard worldwide penis size measurement protocole to be able to compare penis sizes from everywhere.