Conflicting evidence and decisions by agency professionals: an experimental test in the context of merger regulation

Many important regulatory decisions are taken by professionals employing limited and conflicting evidence. We conduct an experiment in a merger regulation setting, identifying the role of different standards of proof, volumes of evidence, cost of error and professional or lay decision making. The experiment was conducted on current practitioners from 11 different jurisdictions, in addition to student subjects. Legal standards of proof significantly affect decisions. There are specific differences because of professional judgment, including in how error costs and volume of evidence are taken into account. We narrow the range of explanations for why professional decision making matters.