[ucaetano]

Yep, and from the link:

The Supreme Court has defined market power as "the ability to raise prices above those that would be charged in a competitive market,"(8) and monopoly power as "the power to control prices or exclude competition."

Those are the tests you need to pass to take action. And measuring that is a highly academic exercise.

Just go talk to the economics professors and consultants that act as experts in those cases.