Also, for the new refereeing system to be considered a "proper" trial or experiment it ideally needs to be compared with the existing refereeing system. That is, the powers-that-be should state clearly what criteria are used to measure "success". Comparisons of these criteria can then be made between, say, the Champions League (control group) and the Europa League matches to see if there are any significant differences when using "4" and "6" officials in Europe's elite cup competitions.