Many scholars (and quite a few judges) have argued that an appellate court’s dissent rate does not necessarily reflect how often the judges agree on the substantive issues coming before them. Judicial behavior models argue that judges decline to dissent even when they disagree with the Court’s decision for a variety of reasons. Appellate judges tend to believe that an appearance of unanimity is worthwhile simply because it weighs against the cynical view that a court’s decisions are solely dependent on its personnel. Since most appellate judges tend to work in relatively close quarters with their colleagues for many years, simple collegiality can suppress dissent. Judge Richard A. Posner has argued that a dissent “usually has no effect on the law” and “tends to magnify the significance of the majority opinion.” Finally, some analysts have argued that since judges do not receive credit against their share of the Court’s majority opinions for any dissents they choose to write, the press of the Court’s workload can reduce the incidence of published dissents, even when one or more of the Justices disagree with the Court’s ultimate decision.
We saw above that dissent is comparatively uncommon on the Appellate Court – between one-in-four and one-in-twenty cases. On the other hand, in most recent years (although there was a curious dip in 2012 and 2013), the Illinois Supreme Court tends to decide at least seventy percent of its civil cases unanimously:
Tomorrow we’ll look more closely at the non-unanimous decisions – specifically, how often is the Court almost evenly divided?
 E.g., Choi and Gulati, “Trading Votes,” 81 S. Cal. L. Rev. 735; Epstein, Landes & Posner, The Behavior of Federal Judges, pp. 255-304; Jennifer L. Peresie, “Female Judges Matter: Gender and Collegial Decisionmaking in the Federal Appellate Courts,” 114 Yale L. Journal 1781-1786 (2005); Harry T. Edwards, “The Effects of Collegiality on Judicial Decision Making,” Univ. Penn. L. Rev. 1645-1652 (May 2003); Evan H. Caminker, “Sincere and Strategic Voting Norms on Multimember Courts.” Mich. L. Rev. 97, no. 8 (1999): 2297-380.
 Richard A. Posner, How Judges Think (Harvard University Press: 2003), p. 32.
 Historical data shows that dissent was relatively uncommon on the United States Supreme Court until the New Deal era. Historical data is sparse on the Federal Circuits and the state Supreme Courts, but one would expect those courts to follow the lead of the Supreme Court.