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

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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

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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. Graph of Martin-Quinn Scores of Supreme Court Justices 1937-Now

Graph of Martin-Quinn Scores of Supreme Court Justices 1937-Now

References

{{reflist Supreme Court of the United States Political spectrum Rating Political science