The graph's x-axis is just the funds sorted in order of their values, right? That fact that that's not the kind of x-axis that you can label and draw points on should indicate to you that the visualization is not ideal.

I think in your title assertion you're confusing "power law" with the "long tail". To verify this relationship you will need an actual x-y plot. The way to get there, from what you are describing, is with binning.

As others have pointed out something like a power law should be on a log-scale graph. When you do bins in an example like this you definitely want to try putting it on a log-log graph. But if you're not sure what you're looking for or demonstrating, you should output both log- and linear-scale graphs for your viewer.