Martin-Quinn scores or M-Q scores are dynamic metrics used to gauge the ideology of a U.S. Supreme Court Justice based on their voting record. Therefore, a jurist's score will continuously change, unlike static measures of ideology such as the
Segal–Cover score A Segal–Cover score is an attempt to measure the "perceived qualifications and ideology" of nominees to the United States Supreme Court. The scores are created by analyzing pre-confirmation newspaper editorials regarding the nominations from ''The ...
and
Judicial Common Space
The Judicial Common Space (JCS) is a strategy to compare the ideologies of American judges. It was developed to compare the viewpoints of judges in the US Supreme Court and the Court of Appeals. It is one of the most commonly used measures of judic ...
score. Martin-Quinn scores are among the most commonly used measures of judicial ideology.
History and method
The concept of the Martin-Quinn score was published in a 2002 paper by
Andrew D. Martin and Kevin M. Quinn.
The Martin-Quinn score uses
Markov chain Monte Carlo
In statistics, Markov chain Monte Carlo (MCMC) methods comprise a class of algorithms for sampling from a probability distribution. By constructing a Markov chain that has the desired distribution as its equilibrium distribution, one can obtain ...
(MCMC) methods to fit a
Bayesian
Thomas Bayes (/beɪz/; c. 1701 – 1761) was an English statistician, philosopher, and Presbyterian minister.
Bayesian () refers either to a range of concepts and approaches that relate to statistical methods based on Bayes' theorem, or a followe ...
model of ideal points. The ideal points can change over time due to the
item response model.
MQ scores are theoretically unbounded (have no minimum or maximum values). MQ scores are dynamic, as each decision made by a judge creates another data point that can be integrated into the model. The MQ score places the justices on a continuum of more liberal to more conservative. As of 2007, scores roughly ranged between -8 and 4, with the lowest score of about -8 attributed to
William O. Douglas
William Orville Douglas (October 16, 1898January 19, 1980) was an American jurist who served as an associate justice of the Supreme Court of the United States, who was known for his strong progressive and civil libertarian views, and is often c ...
(tenure on the USSC from 1939 to 1975) and the highest score of about 4.5 attributed to
William Rehnquist
William Hubbs Rehnquist ( ; October 1, 1924 – September 3, 2005) was an American attorney and jurist who served on the U.S. Supreme Court for 33 years, first as an associate justice from 1972 to 1986 and then as the 16th chief justice from ...
(tenure from 1972 to 2005).
The largest shift in score between judges on the same Supreme Court seat since 1953 came when
Thurgood Marshall
Thurgood Marshall (July 2, 1908 – January 24, 1993) was an American civil rights lawyer and jurist who served as an associate justice of the Supreme Court of the United States from 1967 until 1991. He was the Supreme Court's first African-A ...
(tenure from 1967 to 1990) was replaced by
Clarence Thomas
Clarence Thomas (born June 23, 1948) is an American jurist who serves as an associate justice of the Supreme Court of the United States. He was nominated by President George H. W. Bush to succeed Thurgood Marshall and has served since 199 ...
.
Ward Farnsworth
Ward Farnsworth (born 1967) is Professor of Law and holder of the W. Page Keeton Chair at the University of Texas School of Law, where he was Dean from 2012-2022. He served as Reporter for the American Law Institute’s Restatement of the Law T ...
wrote that while the MQ model has ingenuity and promise, it falls short of proving what it aims to. He criticized the methodology of MQ scores, saying that MQ scores only take into account whether a judge affirms or reverses a ruling, and not the ideological outcome their action supports. In part, "the relationship between the spectrum generated by the
artin-Quinnmodel and the spectrum of policy decisions in the real world is a matter of guesswork. There is no inherent relationship between them.
Application
MQ scores were initially developed to measure and compare the
ideological leanings of current and former U.S. Supreme Court justices. They have since been applied to the judicial systems of other countries, including Argentina, Belgium, Brazil, the Philippines, Portugal, Spain, Taiwan, Turkey and the United Kingdom.
References
{{reflist
Supreme Court of the United States
Political spectrum
Rating
Political science