I was wondering if anyone knew the best way to calculate volatility for the following scenario. Suppose we are taking a snap shot of the top 3 best teams in a league of 30 teams every week for 20 weeks.

For example

Week 1:

1. Team A
2. Team B
3. Team C

Week 2:

1. Team D
2. Team A
3. Team E

Week 3:

1. Team B
2. Team D
3. Team F

...

Week 10:

1. Team F
2. Team C
3. Team G

We only know the top 3 teams and cannot infer anything about the rest of the standings. What would be some methods to calculate volatility of the top 3? Potentially to offer future predictions.