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Diamonds are only found in layers 1-16 so this graph is incorrect. There is also a significant drop of diamond occurrences above layer 13. This graph is an accurate representation of diamond ore per level:
EDIT: I just saw your graph has 5 lvls of bedrock so it is fine. However, the chances of finding a diamond more than 16 lvls above bedrock is pretty much zero.
again, sorry for not looking at your graph closer. It is correct, the levels are all just 5 more than you would get on your Y: coord.
