Confirmation Bias in the United States Supreme Court Judicial Database
The Journal of Law, Economics, & Organization, Forthcoming
47 Pages Posted: 23 Apr 2009 Last revised: 6 Apr 2011
Date Written: March 16, 2011
We ask whether the widely used direction of decision and direction of vote variables in the United States Supreme Court Judicial Database (USSCJD) are contaminated by confirmation bias, or have been affected by expectations about the likely effects of judicial preferences on case outcomes. Using a sample of generally comparable cases, we find evidence that the assignment of issue codes to these cases, codes that govern the subsequent assignment of “direction” to the Court's judgments, is conditional on both case disposition and the known preferences of the deciding court, in the direction predicted by the hypothesis of confirmation bias. We also find that the USSCJD direction variables overstate the effect of judicial preferences and understate the effect of congressional preferences on case outcomes, relative to objectively coded measures of the Court's judgments.
Keywords: judicial politics, Supreme Court, USSCJD, database, confirmation bias, measurement error, coding, issue, judgement, separation of powers, constraint, Congress
JEL Classification: K40, C81
Suggested Citation: Suggested Citation