What decides a player's nationality (flag icon) in Liquipedia?

Is this simply country of birth? Country of residence for the majority of the player's career? Or is this just a reasonably informally controlled thing? (it seems for example obvious : that the liquipedia "nationality" is completely unrelated to the WCS region elligibility criteria) Edit : Perhaps to clarify - There appear to be no rules for this that I can find, what realistically then should it be based on?