This is no doubt off topic but since I don't have a clue what the topic is about and it does mention potties which is what my query is about, here goes:

We in my part of the world are in a serious drought and water-shortage situation. And it came up in a discussion by experts on such matters that American toilets have a 3 inch outlet hole in the bottom while British toilets have a 4-inch hole. It has been recommended that American toilets be banned but they're about $100 cheaper than Brits.

The question is however: why would peoples of similar genetic make-up and presumably similar outputs have such widely varying toilet requirements?

This is the sort of topic one finds oneself pondering when unable to sleep due to indigestion. Please forget it and go back to Potter or whoever.