Are the shows used to keep people happy/quiet (like the Romans used to do with their "bread and circuses" idea, the thought being if the populace were provided with these things they would not rebel). In modern times the circus has adapted as people have turned away from acts involving live animals (lion taming etc). Have the shows in your world had to adapt? If so, how?
Who goes to the shows? Are they readily accessible to all? Who funds them? And if any raise money for charity, what counts as charity in your fictional world? Can your story be set against the backdrop of a show?