Assessing the Influence of Amici on Supreme Court Decision Making

The authors analyze a dataset of indicators of the influence of amicus filings on the decisions of the United States Supreme Court from October Term 2013 through October Term 2018), examining the effect of filings on the prevailing party, on citations to amicus filings, and on sources drawn from amicus filings. The dataset includes 386 cases, 4500 amicus filings, and 22,000 citations in Supreme Court decisions. In some ways, the paper updates scholarship from the turn of the century, when amicus filings were much less prevalent, but it also breaks new ground with the data about citations to amicus filings and sources drawn from amicus filings. The principal findings are (1) the effect of amicus filings on the decision is much more even than it was at the turn of the century, when it was concentrated on bottom-side filings; and (2) the effects of filings are much more noticeable for amicus filers less directly motivated by monetary considerations (academics, think tanks, and the like) and less noticeable for those more directly motivated by monetary considerations (trade associations and businesses)