This is an unknown number. Someone may have forgotten their password or remembered their password again someday in the future. There is no data to consider.
Not entirely unknown because I am pretty sure that people have keep track of bitcoin supply. Although, it's not really worth worrying about it because there's no point because they have no way of knowing if that bitcoin that they label as lost was just frozen for a decade and will be opened when the time it was supposed to be opened is reached.