I hope this is the right place.

I am writing my thesis on Sport industry and I'm currently facing a statistical issue (of course, you'd say, we are in a statistics forum).

I have to demonstrate the independence between revenues and results on the pitch (represented by a numeric coefficient).

I have the data from 2012 to 2015, 4 years, for 33 teams. My hypothesis is that year after year the revenues are less and less dependent from the results on the pitch.

How would you do that? Considering also the small size of the sample.

Thank you very much to anyone that could help me!