Flexing Judicial Muscle: An Empirical Study of Judicial Activism in the Federal Courts

Corey Rayburn Yung - John Marshall Law School

Immediately following President Obama’s nomination of then-Judge Sonia Sotomayor to replace Justice Souter on the United States Supreme Court, critics branded her a “judicial activist” who would work without regard to the “rule of law.”1 Former House Majority Leader Tom DeLay contended that President Obama “couldn’t have appointed a more activist judge,” and that Justice Sotomayor’s activismmade her unqualified for a seat on the Court.2 Karl Rove said the Republicans could win the battle against Justice Sotomayor by “making a clear case against the judicial activism she represents.”3 On the first day of her confirmation hearings, Senator Jeff Sessions, the ranking Republican on the Senate Judiciary Committee, proclaimed Justice Sotomayor to be an “activist judge that threatens the traditional foundation of the U.S. legal system.”5

Creating and applying a measure across such a large population of judges necessitated the collection of a large dataset. Data were gathered from published and unpublished 2008 opinions issued by the First, Second, Third, Fourth, Fifth, Sixth, Seventh, Eighth, Ninth, Tenth, and Eleventh Circuit Courts of Appeals.  The analyzed dataset (Case Database) from those circuits included 30,726 judicial votes from panel decisions.  In addition to the Case Database, a separate database (Judge Database) was constructed which included biographical and other data about individual judges. The Judge Database included data for all federal appellate judges that served on panels included in the Case Database.

Based upon the results of this study using the new dataset, there was a strong correlation between the level of deferencein a standard of review and the rate of reversal. Figure 1, below, illustratesthe reversal rates with the three most commonly applied standards of review, based on all circuits in this study.  The only non-deferential standard in Figure 1 is de novo review.  The other two standards afford deference to the judgments of district courts.  If standards of review were functioning as expected, and not acting as mere window dressing on opinions, it would be expected that reversal rates when using non-deferential standards would be higher than reversal rates when using deferential standards. Indeed, the results described in Figure 1 support that hypothesis.

Given the significant difference in reversal rates between the non-deferential and deferential standards, there was good reason to think that studying reversal rates of different judges using deferential standards would provide a way to capture the elusive baseline associated with judicial activism.  By focusing on the situations in which a judge was expected to defer more frequently to other constitutional actors, a measure was created to determine a judge’s relative activism level in the aggregate.

However, such a measure by itself was incomplete. After all, if ideology is an important predictor of judicial decision-making, as previous studies have indicated, then merely counting instances when a particular judge failed to defer would be insufficient.  A reversal might indicate only an ideological disagreement with a lower court, rather than one based upon a judge’s activism. To address this problem, there was a need toremove the effects of cases decided only by ideology or other factors separate from the concept of activism.  Judicial decisions using non-deferential (de novo) standards provide a means to isolate aggregate activism because a judge is unfettered by the formalist rule of deference in such cases.  Thus, the raw measure of an “Activism Differential” for an individual judge adopted in this study was:

Activism Differential = Reversal rate using de novo standard – Reversal rate using deferential standards

For each judge, a raw Activism Differential was computed.  However, there were four adjustments made to the raw Activism Differentials in order to allow for valid inter-circuit comparisons between judges and comparisons between circuits:the case mixes of judges, panel effects, and circuit differences, and sought to provide a meaningful scale.

Although the Judge Database included data from over 1,400 judges who served on the United States Courts of Appeals, sat by designation on those courts, or had their decisions reviewed by those courts, many of these judges only issued votes in a limited number of cases.  Because the smaller sample sizes of votes for these judges might yield unacceptable error rates, the following analyses examined only the 177 judges who had at least 200 interactions with other judges.  Figure 2 illustrates the distribution of these Activism Scores.

Notably, as indicated in Figure 2, the mean Activism Score was 50.2 and one standard deviation was 21.3 points.

As noted at the opening of this piece, the concept of judicial activism has become so politicized that it has become part of virtually every major discussion concerning the judiciary and individual judges.  Among the various concerns about activism is whether individual Presidents or political parties have been responsible for appointing more activist judges to the United States Courts of Appeals.  Traditionally, judges appointed by Democratic Presidents have been labeled as “activists” who push social agendas on an unwilling public.  However, increasingly there are attacks on Republican appointees for “right-wing judicial activism.”

The data did not support either hypothesis.  As demonstrated in Figure 3 below, for judges who issued opinions in 2008, the data did not indicate that the appointing President had a statistically significant correlation with a judge’s activism.

The Activism Scores of Presidents Carter, Reagan, George H.W. Bush, Clinton, and George W. Bush varied by a mere 6.2 points, which linear regression determined was not statistically significant.

Looking solely at the political party of the appointing President also did not yield results that would support either hypothesis.  Figure 4 below illustrates that Republican and Democrat appointees had similar Activism Scores in the aggregate.

Overall, the appointees of Democratic Presidents exhibited a slightly higher average Activism Score (52.3 versus 48.9), but this difference was not statistically significant based on a linear regression of the Activism Scores and the political party of the appointing President. As a result, the study results provided neither a reason to believe that particular Presidents appoint more or less activist judges nor one to suspect that the political party of the appointing President is related to the activism of judges.

An observer might contend that the limited difference in activism based on the party of the appointing President was due to the prevalence of an ideological split between the Senate and President during the time period when most of the 2008 judges were appointed.  As a corollary, one might expect a higher rate of activism among judges when the President and Senate were of the same party, since the President would be freer to appoint judges that would be more active in support of the President’s ideology.  Thus, the hypothesis would be that unity among the Senate and the President at the time of appointment would produce more activist judges.  However, as Figure 5 indicates, the data did not support this hypothesis.

The data indicated that the party alignment of the Senate and President did not cause a substantial change in the activism of the appointed judge. Again, a linear regression found that the data did not support a statistically significant correlation between a judge’s activism and whether the President and Senate were from the same party at the time of confirmation.

It might also have been possible, even likely, that the President took into account the composition of the Senate before nominating a judge for the Courts of Appeals.  A President might therefore have nominated judges that were closer to the partisan makeup of the Senate in order to ensure confirmation.  A hypothesis would thus contend that the political makeup of the Senate at the time of confirmation would be correlated with the Activism Scores of nominees.  Figure 6 below illustrates the distribution of Activism Scores based upon the number of Republican Senators at the time of the nomination.

As is exhibited in Figure 6, there was no apparent connection between the composition of the Senate at the time of appointment and the judge’s activism.  A linear regression confirmed that the data did not exhibit a statistically significant correlation between the political composition of the Senate at the time of confirmation and a judge’s activism.

Unlike with Supreme Court Justices, there have been very few measures of the ideology of individual judges on the Courts of Appeals.  Nonetheless, existing research has indicated that ideology is a factor in predicting judicial outcomes at the federal level.  A refinement on the appointing-President measure incorporated data about the Senators from the state of the nominated judge.  Lee Epstein, Andrew Martin, Jeffrey Segal, and Chad Westerland calculated, based upon the prior work of other scholars, “common space scores” for individual active judges to measure their ideology.  The common space scores mapped the ideology of judges on the Courts of Appeals on a continuum of the political spectrum, instead of using the binary construction required when looking to the party of the appointing President.  A hypothesis would hold that the ideology of the judge would correlate with activism.  However, as Figure 7 illustrates, there was no obvious connection between judicial ideology as measured by common space scores and activism.

Regression analysis did not reveal a statistically significant relationship between common space scores and activism.  Therefore, even when ideology was computed using the leading measure of the concept, there was no observed connection between judicial ideology and activism.

Judicial activism is a concept that has been used, abused, studied, and debated.  It has become an important and permanent fixture in discussions about American judges and the judiciary.  To give greater coherence and cogency to future debates about such subjects, it is helpful to have empirical data about the concepts of “judicial activism” and “restraint.”

Despite the beliefs of partisans on all sides, there is no evidence of any statistically significant connection between judicial activism and political party.  The results indicated no such evidence of a relationship for the appointing President, the appointing President’s party, or the commonality of party between the President and the majority of the Senate.  The similarities between the activism levels of appointees from different Presidents and political parties poignantly illustrates the degree to which partisan attacks using the activist label are unsupported by the data that have been studied.


Corey Rayburg Yung is an Associate Professor of Law at John Marshall Law School, Visiting Professor of Law at University of Kansas School of Law, and Visiting Professor of Law at University of Iowa College at Law.

Copyright © 2011 Northwestern University School of Law.

This Legal Workshop Piece is based on the following: Corey Rayburn Yung, Flexing Judicial Muscle: An Empirical Study of Judicial Activism in the Federal Courts,
105 NW. U. L. REV. 1 (2011).

  1. See Tom LoBianco, Lawyers Tag Sotomayor as “Terror on the Bench”, WASH. TIMES, May 29, 2009, at A01.
  2. White House Responds as GOP Continues Sotomayor Attacks, CNN (May 29, 2009, 9:13 AM), http://www.cnn.com/2009/POLITICS/05/29/sotomayor.white.house/index.html.
  3. Karl Rove, ‘Empathy’ is Code for Judicial Activism, Wall St. J., May 28, 2009.
  4. Sotomayor Pledges ‘Fidelity to the Law’, CNN (July 13, 2009, 5:57 PM), http://www.cnn.com/2009/POLITICS/07/13/sotomayor.hearing/index.html.
  5. For example, if a judge reverses a district court judgment applying a clear erroneous standard of review, that is more indicative of activism than when utilizing a de novo standard.

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