In L.A. County Flood Control District v. Natural Resources Defense Council, the Supreme Court unanimously reversed a Ninth Circuit holding that navigable water passing through a concrete channel does not constitute "discharge" under the Clean Water Act. (1) This case had the unusual distinction of having the petitioner and respondent agree on the proper judgment. As Justice Ginsburg's majority opinion noted, "the parties and the United States as amicus curiae agree [with the result]." (2) After the Court described the outcome as "hardly surprising" in light of existing precedent, (3) one Supreme Court litigator and commentator publicly wondered "why the Court bothered setting the case for briefing and argument, rather than just summarily reversing, given that all the parties have agreed on the answer to the question presented from the beginning." (4) But the case included another oddity: despite the unanimous judgment, it was not a unanimous opinion because Justice Samuel Alito had it noted without explanation that he "concurs in the judgment." (5)
The silent concurrence is a puzzling institutional practice for several reasons. (6) By definition it provides no explanation for why a Justice agrees with the judgment but refuses to join the majority opinion. As a result, silent concurrences conflict with the norm that opinions are the primary currency by which judges translate their preferences into law. (7) Moreover, this practice is puzzling because Justices have several low-cost alternatives to noting concurrence. As an initial matter, Justices might issue perfunctory opinions that offer a brief explanation for staking out a separate position. As a circuit court judge, for example, Alito once had it noted that he "concurs in the judgment for essentially the reasons given by the District Court." (8) Although readers may have to turn elsewhere, such as to a lower court opinion, for explanation, a perfunctory opinion at least provides some indication of the judge's thinking. Alternatively, there is a long history of Justices silently acquiescing in opinions with which they disagree. (9)
Why do Justices sometimes choose to note their concurrence in the result without explanation rather than go along silently with the majority opinion or write separately? This question has received little attention, most likely because it is inherently difficult to answer without access to private information. Of course, one might observe Justice Alito's silent concurrence in L.A. County Flood Control District and quickly surmise that the case's unusual posture and comparative unimportance had something to do with his decision. (10) But this offers little in the way of explanation. After all, other cases that have unusual postures or are comparatively unimportant do not generate silent concurrences. Moreover, the case's posture or importance does not provide any information about why Alito refused to join the majority opinion. This is also exactly the type of case where we are more likely to observe Justices who disagree with the majority go along silently without publicly indicating any opposition. (11)
In this Article, I leverage private information to explain why Justices silently concur. Specifically, I utilize the private papers of several Justices who served during the Burger Court, OT 1969-OT 1985. (12) Using these private papers, I find that a variety of factors influence decisions to concur silently. Time constraints and perceptions about case importance are among the most important determinants of concurring silently. In addition, silent concurrences may be driven by vote switching and uncertainty about the proper disposition or legal rule, a desire to maintain a consistent voting record and withhold support for disfavored precedents, and bargaining failures over opinion language and scope. Silent concurrences may also be driven by a combination of those factors. Before addressing these determinants in more detail, the next section illuminates the underlying puzzle with a brief discussion of concurring opinions.
WRITTEN VERSUS SILENT CONCURRENCES
Concurring opinions are a mainstay in Supreme Court decision making. As the consensual period of Supreme Court decision making came to a close in the early twentieth century, Justices increased their production of concurring and dissenting opinions. (13) With a regular concurring opinion, a Justice writes separately but also joins the majority opinion; with a special concurring opinion, a Justice agrees with the judgment reached by the majority but disagrees about the justification for reaching that result. Concurring opinions, whether regular or special, come in a variety of forms. They might be written to limit or expand the majority opinion, propose an alternative legal theory, or make an idiosyncratic point. (14)
Written concurrences, like written dissents, are potentially valuable for a number of reasons. As an initial matter, a concurring opinion may prove to be highly influential in the subsequent development of law. Among the best known is Justice Robert H. Jackson's concurrence in Youngstown Sheet & Tube Co. v. Sawyer (15) delineating a three-part framework for analyzing the constitutional validity of unilateral executive actions. (16) Even if the opinion's influence is not immediate, a written concurrence may have downstream effects on the development of law and over time come to be influential.
Of course, Justice Jackson's Youngstown concurrence is the exception not the rule. Most concurrences do not find their way into the constitutional law canon. Nonetheless, it is not uncommon for written concurrences to shape the development of law at the margin. As noted previously, written concurrences can help frame the majority opinion by suggesting limiting or expansive interpretations. Empirical evidence suggests that written concurrences can play an important role in determining the extent to which lower courts comply with majority opinions. (17) Thus, written concurrences can be valuable insofar as they provide signals to lower court judges about how to interpret precedent. More immediately, as Justice Ruth Bader Ginsburg once noted about separate opinions generally, "they may provoke clarifications, refinements, [and] modifications in the court's opinion." (18)
Written concurrences also allow Justices to communicate their sincere preferences. Commentators have long disagreed about the extent to which legal, policy or strategic goals guide judicial decision making. (19) Regardless, Justices that agree with the result of a case but not the reasoning must write separately in order to communicate their sincere preferences. Moreover, as Justice Antonin Scalia once noted, writing separately allows for "writ[ing] an opinion solely for oneself, without the need to accommodate, to any degree whatever, the more-or-less differing views of one's colleagues; to add precisely the points of law that one considers important and no others; to express precisely the degree of quibble, or foreboding, or disbelief, or indignation that one believes the majority's disposition should engender." (20) In this way, separate opinions stand in stark contrast to majority opinions, which are often the product of compromise in order to maintain or enlarge a winning coalition.
Legitimacy and reputation-enhancing effects also flow from separate opinions. (21) This occurs in at least two ways. First, written opinions are the primary currency through which Justices build their reputations. Justices who refuse to write opinions aside from assigned majority opinions miss out on opportunities to enhance their professional standing. Second, written opinions provide a measure of public accountability. Indeed, some judges are required to justify their votes. For example, the California constitution requires "[d]ecisions of the Supreme Court and courts of appeal that determine causes [to]  be in writing with reasons stated." (22) Although Article III judges enjoy life tenure during good behavior, political actors and the public nonetheless play a substantial role in shaping judicial decision making through informal appeals and formal institutional attacks. (23) Obscuring justifications for votes may complicate the task of maintaining or building institutional legitimacy. (24)
All of these justifications for not merely going along with the majority disposition and opinion despite disagreement have one thing in common: benefit accrual requires Justices to write separate opinions. This makes the silent concurrence especially puzzling. Moreover, the existing literature on separate opinion writing lends little insight into why Justices would decide to concur without explanation. Although recent research offers insight into why Justices sometimes silently acquiesce to the majority position despite disagreement, (25) concurring without explanation is a fundamentally different practice insofar as it involves a Justice noting disagreement but refusing to explain the reasons underlying this disagreement. A leading opinion-writing treatise recognizes the practice of silently concurring, but criticizes it for "cast[ing] doubt on the principles declared in the main opinion without indicating why they are wrong or questionable." (26)
The most comprehensive study of noting disagreement without explanation focuses exclusively on Justice William O. Douglas's voting behavior in tax cases and other select matters concerning economic regulation. (27) Although sometimes remembered first for his colorful public law opinions, Douglas came to the Court with considerable experience in private law fields such as business organizations and finance. (28) Drawing on the economic expertise he developed in private practice, as a professor at Yale Law School, and as Chairman of the Securities and Exchange Commission, Justice Douglas made substantial contributions to the Court's jurisprudence on corporate...