It turned out the published articles tipped the scales: Getting a public Wikipedia article increased a case's citations by more than 20 percent. The increase was statistically significant, and the effect was particularly strong for cases that supported the argument the citing judge was making in their decision (but not the converse). Unsurprisingly, the increase was bigger for citations by lower courts -- the High Court -- and mostly absent for citations by appellate courts -- the Supreme Court and Court of Appeal. The researchers suspect this is showing that Wikipedia is used more by judges or clerks who have a heavier workload, for whom the convenience of Wikipedia offers a greater attraction.
"To our knowledge, this is the first randomized field experiment that investigates the influence of legal sources on judicial behavior. And because randomized experiments are the gold standard for this type of research, we know the effect we are seeing is causation, not just correlation," says Thompson, the lead author of the study. "The fact that we wrote up all these cases, but the only ones that ended up on Wikipedia were those that won the proverbial 'coin flip,' allows us to show that Wikipedia is influencing both what judges cite and how they write up their decisions." "Our results also highlight an important public policy issue," Thompson adds. "With a source that is as widely used as Wikipedia, we want to make sure we are building institutions to ensure that the information is of the highest quality. The finding that judges or their staffs are using Wikipedia is a much bigger worry if the information they find there isn't reliable."The paper describing the study has been published in " The Cambridge Handbook of Experimental Jurisprudence."