Must the money be split evenly between the three Worldcons?
It’s not required by the agreement, but it is highly desirable, and Worldcons should make a good-faith effort to split PAF evenly. A case where that would not be possible might be if a Worldcon received a significant refund more than a year after the convention so that the immediately succeeding convention had already occurred (and was in the black) and had no use for PAF. The Worldcon would still have an obligation to pass along at least 50% of that profit, but there would be no way this could be done evenly.