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There will be no definitive data for this that we can get. Betting sites will also not reveal everything because that would clearly show how much profit the betting provider makes, rather than the big chance of long-term profit that the bettor has.
Specific data will be a casino secret and of course will not be disclosed to the public, maybe only some supporting data will be disclosed.
But legal online casino sites will disclose data in accordance with established regulations,
so local jurisdictions must know how the casino works and who enters and exits or stays in the casino.
I think this is true, because if casinos collected this data and posted it in full detail, then it would be possible to have a general picture and understand how little players actually win. Probably, these numbers are presented to the public once again, not in the most detailed form, and not all casinos. However, I think betting professionals have such information through familiar casino owners who share such statistics with them, and who knows, maybe this happens for money, I don’t know, but these are just my guesses.