The leniency rule revisited: Experiments on cartel formation with open communication

•We study cartel formation when free-form open communication is freely available.•A participant in the role of the authority judges conduct during the experiment.•The authority’s payment depends on overlap with a cartel expert’s judgment.•We find that a leniency rule does not affect cartelization or prices.•We argue that open communication counteracts the destabilizing effect of leniency.