Judging by how I usually stock my own tanks, most other people overstock their tanks. That is, of course, a totally meaningless statement unless you have seen my tanks. I do not use the inch per gallon rule, I look at the tank and notice how much room each fish seems to own for himself alone. If it seems too small for his size, it is overstocked. If it looks like lots of elbow room, it is not over stocked. I have no easy way to quantify my results because I don't have a real rule to go by. When someone on here asks if they are overstocked, I try to imagine the picture that tank would present to me and then answer the question. I will often resort to the inch per gallon rule if it is obviously being violated but that is not how I arrive at the right answer. IMO, there is no substitute for the experience of having kept fish with success through all of the power outages and other mishaps to giving you a feel for proper stocking. When I see people talk about having plenty of circulation and filtration to allow heavy stocking, my first inclination is to ask how the fish will do in the next power outage. I usually hold back because I know my idea of a good stocking level looks like a bare tank to most people.
I now have this vision of someone sunning themselves on a beach sun lounger, a deckchair next to them with a little fish tank containing fry - all with their shades on LOL and slapping sunscreen on each other 
