2 questions: 1. How would anyone be able to calculate intraday, dynamic open interest and its composition? 2. How would it be useful? Those already in can't affect price until they decide to get out or reverse. Those out on the sidelines can't affect price until they decide to get in. In other words does the size of open interest matter? Thinking further, it would be interesting to see open interest pulsing away - on big moves I imagine it erodes over time which may give you some clue on the timing of the next turn.