Well, it wasn't me who created those numbers, but they are interesting.
Any way you could show the source for that info?
Sure! Here is the source for those numbers between 9000 BC and 540 AD (actually until 1845 AD):
politics.ie/threads/the-population-of-ireland-from-ancient-times-until-the-great-famine.156856/
^^^
Maybe you guys can contact each other and publish a joint estimate since 9000 BC till present?
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This is also a good source but some numbers might be too low (check the chapter about Ireland):
/Teaching/Histpop/Reading/Atlas%20of%20World%20Pop%20History%20McEvedy&Jones.pdf