I'd read that before and I enjoyed it all over again; thank you! It makes a lot of sense! I suppose the main difference between our two theories is that I have only the top and bottom few percent being moved, and people being able to choose a lower grade. The only things I'm not sure about are the disruption to family life and the destabilising of society, and Avon wanting to find Delta parents. I think he'd prefer to think of himself as always superior.