Efficiency gap

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The phrase efficiency gap refers to a method for determining whether partisan gerrymandering has occurred in a jurisdiction. Devised by law professor Nicholas Stephanopoulos and research fellow Eric McGhee in 2015, the efficiency gap is defined as "the difference between [political parties'] wasted votes, divided by the total number of votes cast in the election." In this context, wasted votes are defined as any votes that were cast for the losing party and any votes in excess of 50 percent of the total vote that were cast for the winning party.

On November 21, 2016, a federal district court ruled that the map for the Wisconsin State Assembly constituted an illegal partisan gerrymander. In its decision, the court accepted the application of the efficiency gap metric, which was employed by the plaintiffs in their arguments. The decision was appealed to the Supreme Court of the United States, which, on June 19, 2017, agreed to hear the case (Gill v. Whitford). The high court heard oral arguments for the case on October 3, 2017. On June 18, 2018, the Supreme Court of the United States remanded the case to the district court for further proceedings, finding that the plaintiffs had failed to demonstrate standing to bring a complaint under Article III of the United States Constitution.

The sections below provide further information about the efficiency gap:

1. Background: This section defines the phrase efficiency gap, discusses its application, and provides examples of its calculation.
2. Legal context: This section describes the broader legal context surrounding the issue of partisan gerrymandering. Two cases (Vieth v. Jubelirer and Gill v. Whitford) are discussed.
3. Support and opposition: This section outlines a sample of the arguments made in support of and in opposition to the application of the efficiency gap as a standard for measuring partisan gerrymandering.

Background

In a 2015 article for the University of Chicago Law Review, Nicholas Stephanopoulos, then an assistant professor of law at the University of Chicago Law School, and Eric McGhee, then a research fellow at the Public Policy Institute of California, defined the efficiency gap as a concept and proposed that the metric be applied to determine whether illegal partisan gerrymandering has occurred in a jurisdiction.

Definition

In their article on the subject, Stephanopoulos and McGhee described the goal of partisan gerrymandering as follows:

“	The goal of partisan gerrymandering is to win as many seats as possible given a certain number of votes. To accomplish this aim, a party must ensure that its votes translate into seats more 'efficiently' than do those of its opponent. In the plurality-rule, single-member district elections that are almost universal in American politics, 'inefficient' votes are those that do not directly contribute to victory. Thus, any vote for a losing candidate is wasted by definition, but so too is any vote beyond the 50 percent threshold needed (in a two-candidate race) to win a seat. If these supporters could be moved through redistricting to a different seat, they could help the party claim that seat as well without changing the outcome in the seat from which they were moved.	”
—Nicholas O. Stephanopoulos and Eric M. McGhee

Granting that some inefficient votes (as defined above) exist in any single-member district electoral system, Stephanopoulos and McGhee posited that the goal of a party conducting a partisan gerrymander is to "end up with fewer wasted votes than the opposition by winning its seats by smaller margins on average." Working from these premises, Stephanopoulos and McGhee defined the efficiency gap as "the difference between the parties' respective wasted votes, divided by the total number of votes cast in the election."

Application

Stephanopoulos and McGhee proposed that the efficiency gap be expressed as a number of seats when evaluating congressional maps and as a ratio when used for evaluating state legislative maps. They reasoned that "what matters in congressional plans is their impact on the total number of seats held by each party at the national level." By contrast, Stephanopoulos and McGhee wrote, "state houses are self-contained bodies of varying sizes, for which seat shares reveal the scale of parties' advantages and enable temporal and spatial comparability." Stephanopoulos and McGhee proposed that efficiency gaps of two seats (in the case of congressional delegations) and 8 percent (in the case of state legislative chambers) be used as minimum thresholds for determining whether an unconstitutional partisan gerrymander has taken place.

Example

The table below presents hypothetical vote totals for two parties vying for seats in five districts. Wasted votes come in two varieties: lost votes and excess votes. Lost votes are defined as all votes cast for the losing party. Excess votes are defined as all votes in excess of 50 percent cast for the winning party.

Hypothetical vote totals for efficiency gap calculations
Example	Total votes by party		Lost votes by party		Excess votes by party		Wasted votes by party
	Party 1	Party 2	Party 1	Party 2	Party 1	Party 2	Party 1	Party 2
District A	600	400	0	400	100	0	100	400
District B	400	600	400	0	0	100	400	100
District C	550	450	0	450	50	0	50	450
District D	600	400	0	400	100	0	100	400
District E	575	425	0	425	75	0	75	425
Totals	2,725	2,275	400	1,675	325	100	725	1,775

As demonstrated in the table above, Party 1 won four seats and wasted 725 votes. By contrast, Party 2 won one seat and wasted 1,775 votes, 1,050 more votes than Party 1. Taking the wasted vote discrepancy (1,050) and dividing by the total number of votes cast for both parties in all five districts (5,000), the efficiency gap equals 21 percent in favor of Party 1.

Legal context

In contrast with racial gerrymandering, on which the Supreme Court of the United States has issued rulings in the past affirming that such practices violate federal law, the high court had not, as of June 2018, issued a ruling establishing clear precedent on the question of partisan gerrymandering. Although the court has granted in past cases that partisan gerrymandering can violate the United States Constitution, it has never adopted a standard for identifying or measuring partisan gerrymanders (the efficiency gap being a proposal for such a standard). According to The Wall Street Journal, in an article discussing Gill v. Whitford (see below) "some Supreme Court justices have previously expressed concern about partisan gerrymandering, but a majority of the court has been hesitant to intervene so directly in the American political process and to say how much partisanship is too much." Robert Barnes, writing on June 19, 2017, for The Washington Post, made a similar observation: "[The] Supreme Court has long been tolerant of partisan gerrymandering – and some justices have thought that the court shouldn't even be involved."

Two cases touching on the question of partisan gerrymandering are discussed below. The first, Vieth v. Jubelirer, was decided by the Supreme Court of the United States in 2004. In this ruling, a divided court declined to intervene directly in a case involving alleged partisan gerrymandering. Associate Justice Antonin Scalia penned a plurality opinion in which he proposed that federal law does not establish a "judicially enforceable limit on the political considerations that the States and Congress may take into account when districting." Three other justices joined in this opinion. The remaining five justices issued separate opinions; in all five, the justices allowed for the possibility of a judicially enforceable limitation against partisan gerrymandering. The second, Gill v. Whitford, was decided by a federal district court in 2016. The district court ruled that Wisconsin state lawmakers had conducted an illegal partisan gerrymander of the state assembly district map. In its decision, the court cited efficiency gap calculations. The case was appealed to the Supreme Court, which announced on June 19, 2017, that it would hear the case. On June 18, 2018, the court ruled that the plaintiffs had failed to demonstrate standing under Article III of the United States Constitution to bring a complaint. The court did not address the broader question of whether partisan gerrymandering claims are justiciable, instead remanding the cast to the district court for further proceedings.

Vieth v. Jubelirer (2004)

Vieth v. Jubelirer was a case decided by the Supreme Court of the United States in 2004. The case was brought by a group of Pennsylvania Democrats who alleged that the state legislature, controlled by Republicans at the time of the 2000 redistricting cycle, had developed a congressional district map that constituted an illegal partisan gerrymander. The plaintiffs alleged that the map "violated the one-person, one-vote principle of Article 1, Section 2, of the Constitution, the Equal Protection clause, the Privileges and Immunities clause, and the freedom of association [clause]." According to Oyez, a federal district court "found the act unconstitutional because it created districts with different numbers of voters, thereby violating the one-person, one-vote principle. Because the plaintiffs had shown that it was possible to create districts with smaller differences, and because the defendants had failed to justify the disparities resulting under their plan, it was therefore unconstitutional." The case was appealed to the Supreme Court of the United States. At issue in the case were the following questions:

“	Can voters affiliated with a political party sue to block implementation of a Congressional redistricting plan by claiming that it was manipulated for purely political reasons? Does a state violate the Equal Protection clause of the 14th Amendment when it disregards neutral redistricting principles (such as trying to avoid splitting municipalities into different Congressional districts) in order to achieve an advantage for one political party? Does a state exceed its power under Article I of the Constitution when it draws Congressional districts to ensure that a minority party will consistently win a super-majority of the state's Congressional seats?	”
—Oyez

Justice Antonin Scalia penned the plurality opinion in Vieth v. Jubelirer.

On April 28, 2004, the court issued a split decision with no majority opinion, declining to intervene in the case. Five justices – Chief Justice William Rehnquist and Associate Justices Anthony Kennedy, Sandra Day O'Connor, Antonin Scalia, and Clarence Thomas – voted not to intervene in the particular case. Of these five, all but Kennedy signed onto a plurality opinion penned by Scalia. Referring to Davis v. Bandemer, a 1986 decision in which the high court ruled that partisan gerrymandering claims can be tried in court under the Equal Protection Clause, Scalia wrote the following in the court's plurality opinion:

“	We conclude that neither Article I, §2, nor the Equal Protection Clause, nor (what appellants only fleetingly invoke) Article I, §4, provides a judicially enforceable limit on the political considerations that the States and Congress may take into account when districting. ... Eighteen years of essentially pointless litigation have persuaded us that Bandemer is incapable of principled application. We would therefore overrule that case, and decline to adjudicate these political gerrymandering claims.	”
—Associate Justice Antonin Scalia

In his concurring opinion, Kennedy wrote, "[The] Court's own responsibilities require that we refrain from intervention in this instance. The failings of the many proposed standards for measuring the burden a gerrymander imposes on representational rights make our intervention improper. If workable standards do emerge to measure these burdens, however, courts should be prepared to order relief."

Associate Justice David Souter, joined by Associate Justice Ruth Bader Ginsburg, penned a dissenting opinion supporting the court's earlier ruling in Davis v. Bandemer that partisan gerrymandering claims are justiciable under the Equal Protection Clause (Souter's opinion also proposed a new test for proving claims of illegal partisan gerrymandering). Associate Justices Stephen Breyer and John Paul Stevens penned separate dissents, both asserting the justiciability of partisan gerrymandering claims.

Gill v. Whitford (2016-2017)

In June 2012, Democrats assumed a one-vote majority in the Wisconsin State Senate as the result of a series of recall elections. Although Democrats lost the majority five months later, they were able, in the meantime, to compel law firm Michael Best and Friedrich to turn over files related to the 2011 redistricting cycle (Republicans tasked with drafting new maps in 2011 worked out of the Michael Best and Friedrich office in Madison, Wisconsin). Before Democrats assumed the majority, they had asked Michael Best and Friedrich to turn over the requested records, but the firm refused, saying that it answered to the majority leader. Democrats used these records as evidence when they filed suit in federal district court, alleging that the Wisconsin State Assembly map treated voters "unequally, diluting their voting power based on their political beliefs, in violation of the Fourteenth Amendment's guarantee of equal protection." On November 21, 2016, the United States District Court for the Western District of Wisconsin struck down the district map for the Wisconsin State Assembly, finding in favor of the plaintiffs, a group of state Democrats. The court ruled 2-1 on the matter, with Judges Kenneth Ripple and Barbara Crabb forming the majority. Ripple wrote the following in the court's majority opinion:

“	We find that Act 43 [the redistricting plan enacted by the state legislature in 2011] was intended to burden the representational rights of Democratic voters throughout the decennial period by impeding their ability to translate their votes into legislative seats. Moreover, as demonstrated by the results of the 2012 and 2014 elections, among other evidence, we conclude that Act 43 has had its intended effect.	”
—Judge Kenneth Ripple

Judge William Griesbach dissented and wrote the following in his dissent:

“	I am unable to accept proof of intent to act for political purposes as a significant part of any test for whether a task constitutionally entrusted to the political branches of government is unconstitutional. If political motivation is improper, then the task of redistricting should be constitutionally assigned to some other body, a change in law we lack any authority to effect.	”
—Judge William Griesbach

The court declined to order a remedy when it issued its ruling. Instead, the court ordered the parties involved in the case to submit briefs outlining recommended remedies within 30 days.

The plaintiffs in the case proposed a three-part test for determining whether illegal partisan gerrymandering has occurred in a state.

1. Intent: "Plaintiffs would have to establish that a state had an intent to gerrymander for partisan advantage."
2. Effect: "Plaintiffs would need to prove a partisan effect by proving that the efficiency gap for a plan exceeds a certain numerical threshold."
3. State interest: "Plaintiffs placed the burden on the defendants to rebut the presumption by showing that the plan 'is the necessary result of a legitimate state policy, or inevitable given the state's underlying political geography.'"

Peter Barca (D), the minority leader of the Wisconsin State Assembly, said, "This is an historic victory for voters and further admonishment of the extremely slanted maps that trample the democratic will of the people of Wisconsin." Assembly Speaker Robin Vos (R) said, "There are only two things that are certain about this case: it's unprecedented and it isn't over. The state of Wisconsin has competitive legislative districts that meet every traditional principle of redistricting. Republicans win elections because we have better candidates and a better message that continues to resonate with the voters."

On January 27, 2017, the court ordered state lawmakers to draft a remedial redistricting plan for use in the November 2018 election. The court ordered that this plan be adopted by the legislature and signed into law by the governor by November 1, 2017. On March 24, 2017, state attorneys petitioned the Supreme Court of the United States to reverse the district court's ruling.

On June 19, 2017, the Supreme Court of the United States announced that it would hear the case, Gill v. Whitford. The court also voted 5-4 to stay the district court decision that ordered Wisconsin lawmakers to draft new maps by November 1, 2017. Chief Justice John Roberts and Associate Justices Clarence Thomas, Anthony Kennedy, Samuel Alito, and Neil Gorsuch voted to stay the district court order. Associate Justices Ruth Bader Ginsburg, Elena Kagan, Sonia Sotomayor, and Stephen Breyer dissented. Oral argument in the case took place on October 3, 2017. On June 18, 2018, the Supreme Court of the United States ruled that the plaintiffs had failed to demonstrate standing to bring the complaint under Article III of the United States Constitution. The court's opinion, penned by Roberts, did not address the broader question of whether partisan gerrymandering claims are justiciable and remanded the case to the lower court for further proceedings. Roberts was joined in the majority opinion by Kennedy, Ginsburg, Breyer, Alito, Sotomayor, and Kagan. Kagan wrote a concurring opinion joined by Ginsburg, Breyer, and Sotomayor. Thomas authored an opinion that concurred in part with the majority opinion and in the judgment, joined by Gorsuch.

In response to the ruling, Bill Whitford, a plaintiff in the suit, said, "The discouraging thing is just the delay. We have a road map forward ... I don't think we'll have any difficulty meeting the burdens the court asked us to meet." Wisconsin Solicitor General Misha Tseytlin doubted the viability of a further challenge, saying, "I think it is quite notable that [the plaintiffs] put together a failry large, well-funded litigation team, had a four-day trial, and the Supreme Court unanimously held 9-0 they did not prove the basis of standing. The plaintiffs here failed to prove up the minimal standing to even bring a lawsuit."

On September 14, 2018, in response to the high court's ruling in Gill, the plaintiffs filed an amended complaint in the United States District Court for the Western District of Wisconsin. Also on September 14, 2018, the Wisconsin Assembly Democratic Committee filed a similar but separate suit in the same court.

Support and opposition

Support

Nicholas Stephanopoulos, writing for New Republic in 2014, encouraged courts to adopt the efficiency gap as a means of measuring partisan gerrymandering:

“	The efficiency gap has several properties that make it ideal for measuring the extent of gerrymandering. First, it directly captures the packing and cracking that are at the heart of every biased plan. Surplus votes for winning candidates are the definition of packing, and lost votes for defeated candidates the essence of cracking. ... Second, as an arithmetical matter, the efficiency gap represents a party’s undeserved seat share: the extra fraction of seats a party wins relative to a neutral plan. ... Third, the efficiency gap can be calculated for any election, no matter how uncompetitive. ... And fourth, the gap is computed using actual rather than hypothetical election results.	”
—Nicholas O. Stephanopoulos

Laura Royden and Michael Li, in a report for the Brennan Center for Justice, suggested that the relative simplicity of the efficiency gap metric recommends its application as a standard for determining whether partisan gerrymandering has occurred:

“	The efficiency gap is appealing as a gerrymandering standard because of its simplicity: it is both easy to calculate (requiring only raw vote totals) and easy to understand (producing a disparity in terms of seats). People without strong backgrounds in statistics or redistricting can easily understand the measure, making it a compelling standard.	”
—Laura Royden and Michael Li

Ian Millhiser, writing for ThinkProgress, argued that the efficiency gap metric presented courts with a broadly applicable, objective tool for determining whether illegal partisan gerrymanders have occurred in a jurisdiction:

“	[The efficiency gap] offers what Justice [Anthony] Kennedy described as a 'workable standard'–an objective test that can be used by judges across the country to sort suspect maps from permissible ones. A hundred different judges can examine the same maps and, provided that they are all skilled at arithmetic, all reached identical conclusions about which maps fall within an acceptable range and which ones should be presumed to be unconstitutional	”
—Ian Millhiser

Opposition

Peter Schuck, an emeritus professor of law at Yale University, wrote the following in a guest post for Election Law Blog:

“	This 'efficiency gap' test for partisan gerrymanders is plausible; indeed, some election law scholars and state courts have endorsed it. Even so, the Supreme Court should proceed with caution, skeptical of any such simple, “one-size-fits-all” solution. Here’s why. Increased clustering of partisans in discrete communities would assure many wasted votes even with no packing. Also, the test’s outcome can turn on slight changes in the distribution of votes among districts. It would also protect bipartisan gerrymanders protecting both parties’ incumbents from competition; they tend to have low efficiency gaps. The efficiency gap test, moreover, cannot easily account for how independent voters, third-party voters, and party-switching might make past voting a less reliable guide to predicting future efficiency gaps.	”
—Peter Schuck

Judicial Watch and the Allied Educational Foundation, in an amicus brief filed with the Supreme Court of the United States on behalf of the appellants in Gill v. Whitford, argued that the efficiency gap metric fails to account for redistricting principles (e.g., contiguity, compactness, etc.), as well as the competing variables outside of gerrymandering that might result in a close election:

“	More generally, the 'efficiency gap' approach is flawed because it looks at the wrong indicators of partisan gerrymandering and ignores the right ones. Its use would import a new proportionality requirement into the constitutional law of redistricting. It gives undue weight to the outcomes of close elections, which may have nothing to do with gerrymandering. Meanwhile, it fails to see the violations of traditional districting criteria that have always been recognized as the distinctive marks of partisan gerrymandering.	”
—Judicial Watch and the Allied Educational Foundation

Mitch Kokai, writing for the Carolina Journal, suggested that voters sometimes make decisions that contradict statistical projections, thereby complicating the effectiveness and applicability of the efficiency gap metric:

“	While clever, the efficiency gap statistic strikes this observer as problematic. ... [The] concept is based on the notion that both major political parties control a bloc of votes and that votes not cast for those partes' preferred candidates are 'wasted.' But that's not how elections work. Yes, the two major political parties can use voter registration data and past election results to gauge how many votes they might expect to win in a particular election district. They don't control those votes. Voters control those votes. And their voting decisions can defy statistical models.	”
—Mitch Kokai

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