Right now it looks too easy and obvious answers. You need something that is not always in public and at the end of the round you will ask the campaign manager to validate the prediction. Use calendar week. Like right now we are in week # 32 so this prediction game will stay x weeks long and the week starts from calendar week # 33 or week #34. The questions can be like:

- Which manager will send highest total payout and the campaign name.
- Name three manager who will pay total highest payout in a week in the given calendar time frame from highest to lower.
- Which manager will pay highest number of participants in a week and the campaign name
- Which manager will pay lowest number of participants and the campaign name

These are just some idea, feel free to improve yourself :-)
I think this will make the game more interesting as the participants really needs to do their analysis and post their prediction.