NOMINATE (scaling method) - AbsoluteAstronomy.com

NOMINATE is a multidimensional scaling

Multidimensional scaling

Multidimensional scaling is a set of related statistical techniques often used in information visualization for exploring similarities or dissimilarities in data. MDS is a special case of ordination. An MDS algorithm starts with a matrix of item–item similarities, then assigns a location to each...

method developed by political scientists Keith T. Poole and Howard Rosenthal in the early 1980s to analyze
preferential and choice data, such as legislative roll-call voting behavior. As computing capabilities grew, Poole and Rosenthal developed multiple iterations of their NOMINATE procedure: the original D-NOMINATE method, W-NOMINATE, and most recently DW-NOMINATE (for dynamic, weighted NOMINATE). In 2009, Poole and Rosenthal were named the first recipients of the Society for Political Methodology's Best Statistical Software Award for their development of NOMINATE, a recognition conferred to "individual(s) for developing statistical software that makes a significant research contribution."

Procedure

Though there are important technical differences between these types of NOMINATE scaling procedures; all operate under the same fundamental assumptions. First, that alternative choices can be projected on a basic, low-dimensional (often two-dimensional) Euclidian space. Second, within that space, individuals have utility functions which are bell-shaped (normally distributed), and maximized at their ideal point. Because individuals also have symmetric, single-peaked utility functions

Utility

In economics, utility is a measure of customer satisfaction, referring to the total satisfaction received by a consumer from consuming a good or service....

which center on their ideal point, ideal points represent individuals' most preferred outcomes. That is, individuals most desire outcomes closest their ideal point, and will choose/vote probabilistically for the closest outcome.

Ideal points can be recovered from observing choices, with individuals exhibiting similar preferences placed more closely than those behaving dissimilarly. It is helpful to compare this procedure to producing maps based on driving distances between cities. For example, Los Angeles is about 1,800 miles from St. Louis; St. Louis is about 1,200 miles from Miami; and Miami is about 2,700 miles from Los Angeles. From this (dis)similarities data, any map of these three cities should place Miami far from Los Angeles, with St. Louis somewhere in between (though a bit closer to Miami than Los Angeles). Just as cities like Los Angeles and San Francisco would be clustered on a map, NOMINATE places ideologically similar legislators (e.g., liberal Senators Barbara Boxer (D-CA)

Barbara Boxer

Barbara Levy Boxer is the junior United States Senator from California . A member of the Democratic Party, she previously served in the U.S. House of Representatives ....

and Al Franken (D-MN)

Al Franken

Alan Stuart "Al" Franken is the junior United States Senator from Minnesota. He is a member of the Minnesota Democratic-Farmer-Labor Party, which affiliates with the national Democratic Party....

) closer to each other, and farther from dissimilar legislators (e.g., conservative Senator Tom Coburn (R-OK)

Tom Coburn

Thomas Allen "Tom" Coburn, M.D. , is an American politician, medical doctor, and Southern Baptist deacon. A member of the Republican Party, he currently serves as the junior U.S. Senator from Oklahoma. In the Senate, he is known as "Dr. No" for his tendency to place holds on and vote against bills...

) based on the degree of agreement between their roll call voting records. At the heart of the NOMINATE procedures (and other multidimensional scaling methods

Multidimensional scaling

, such as Poole's Optimal Classification method) are algorithms they utilize to arrange individuals and choices in low dimensional (usually two-dimensional) space. Thus, NOMINATE scores provide "maps" of legislatures.
Using NOMINATE procedures to study congressional roll call voting behavior from the First Congress to the
present-day, Poole and Rosenthal published Congress: A Political-Economic History of Roll Call Voting in 1997 and the revised edition Ideology and Congress in 2007. Both were landmark works for their development and application of the use of sophisticated measurement and scaling methods in political science. These works also revolutionized the study of the American politics and, in particular, Congress. Their methods provided political scientists--for the first time--quantitative measures of Representatives' and Senators' ideology across chambers and across time.

Poole and Rosenthal demonstrate that--despite the many complexities of congressional representation and politics--roll call voting in both the House and the Senate can be organized and explained by no more than two dimensions throughout the sweep of American history. The first dimension (horizontal or x-axis) is the familiar left-right (or liberal-conservative) spectrum on economic matters. The second dimension (vertical or y-axis) picks up attitudes on cross-cutting, salient issues of the day (which include or have included slavery, bimetallism, civil rights, regional, and social/lifestyle issues). For the most part, congressional voting is uni-dimensional, with most of the variation in voting patterns explained by placement along the liberal-conservative first dimension.

Interpreting scores

For illustrative purposes, consider the following plots which use W-NOMINATE scores to scale members of Congress and uses the probabilistic voting model (in which legislators further from the “cutting line” between “yea” and “nay” outcomes become more likely to vote in the predicted manner) to illustrate some major Congressional votes in the 1990s. Some of these votes, like the House’s vote on President Clinton’s

Bill Clinton

William Jefferson "Bill" Clinton is an American politician who served as the 42nd President of the United States from 1993 to 2001. Inaugurated at age 46, he was the third-youngest president. He took office at the end of the Cold War, and was the first president of the baby boomer generation...

welfare reform package (the Personal Responsibility and Work Opportunity Act of 1996

Personal Responsibility and Work Opportunity Act

The Personal Responsibility and Work Opportunity Reconciliation Act of 1996 is a United States federal law considered to be a fundamental shift in both the method and goal of federal cash assistance to the poor. The bill added a workforce development component to welfare legislation, encouraging...

) are best modeled through the use of the first (economic liberal-conservative

Left-Right politics

The left–right political spectrum is a common way of classifying political positions, political ideologies, or political parties along a one-dimensional political spectrum. The perspective of Left vs. Right is a binary interpretation of complex questions...

) dimension. On the welfare reform vote, nearly all Republicans joined the moderate-conservative bloc of House Democrats in voting for the bill, while opposition was virtually confined to the most liberal

Liberalism in the United States

Liberalism in the United States is a broad political philosophy centered on the unalienable rights of the individual. The fundamental liberal ideals of freedom of speech, freedom of the press, freedom of religion for all belief systems, and the separation of church and state, right to due process...

Democrats in the House. The errors (those representatives on the “wrong” side of the cutting line which separates predicted “yeas” and predicted “nays”) are generally close to the cutting line, which is what we would expect. A legislator directly on the cutting line is indifferent between voting “yea” and “nay” on the measure. All members are shown on the left panel of the plot, while only errors are shown on the right panel:
Economic ideology

Economic ideology

An economic ideology distinguishes itself from economic theory in being normative rather than just explanatory in its approach. It expresses a perspective on the way an economy should be run and to what end, whereas the aim of economic theories is to create accurate explanatory models...

also dominates the Senate vote on the Balanced Budget Amendment of 1995

Balanced Budget Amendment

A balanced-budget amendment is a constitutional rule requiring that the state cannot spend more than its income. It requires a balance between the projected receipts and expenditures of the government....

:
On other votes, however, a second dimension (which has recently come to represent attitudes on cultural and lifestyle issues

Culture war

The culture war in American usage is a metaphor used to claim that political conflict is based on sets of conflicting cultural values. The term frequently implies a conflict between those values considered traditionalist or conservative and those considered progressive or liberal...

) is important. For example, roll call votes on gun control

Gun control

Gun control is any law, policy, practice, or proposal designed to restrict or limit the possession, production, importation, shipment, sale, and/or use of guns or other firearms by private citizens...

routinely split party coalitions, with socially conservative “blue dog” Democrats joining most Republicans in opposing additional regulation and socially liberal Republicans

Rockefeller Republican

Rockefeller Republican refers to a faction of the United States Republican Party who held moderate to liberal views similar to those of Nelson Rockefeller...

joining most Democrats in supporting gun control. The addition of the second dimension accounts for these inter-party differences, and the cutting line is more horizontal than vertical (meaning the cleavage is found on the second dimension rather than the first dimension on these votes) This pattern was evident in the 1991 House vote to require waiting periods on handguns:

Political polarization

Poole and Rosenthal (beginning with their 1984 article "The Polarization of American Politics") have also used NOMINATE data to show that, since the 1970s, party delegations in Congress have become ideologically homogeneous and distant from one another (a phenomenon known as "polarization.") Using DW-NOMINATE scores (which permit direct comparisons between members of different Congresses across time), political scientists have demonstrated the expansion of ideological divides in Congress, which has spurred intense partisanship between Republicans and Democrats in recent decades. Contemporary political polarization has had important political consequences on American public policy, as Poole and Rosenthal (with fellow political scientist Nolan McCarty) show in their book Polarized America: The Dance of Ideology and Unequal Riches. The Voteview Blog tracks some of the more notable contemporary consequences of polarization on American politics and public policy.

Applications

NOMINATE has been used to test, refine, and/or develop wide-ranging theories and models of the United States Congress. In Ideology and Congress (pp. 270-271), Poole and Rosenthal agree that their findings are consistent with the "party cartel" model that Cox and McCubbins present in their 1993 book Legislative Leviathan. Keith Krehbiel utilizes NOMINATE scores to determine the ideological rank order of both chambers of Congress in developing his "pivotal politics" theory, as do Gary Cox and Matthew McCubbins in their tests of whether parties in Congress meet the conditions of responsible party government (RPG).

NOMINATE scores are also used by popular media outlets like The New York Times and The Washington Post as a measure of the political ideology of political institutions and elected officials or candidates. Political blogger Nate Silver

Nate Silver

Nathaniel Read "Nate" Silver is an American statistician, psephologist, and writer. Silver first gained public recognition for developing PECOTA, a system for forecasting the performance and career development of Major League Baseball players, which he sold to and then managed for Baseball...

regularly uses DW-NOMINATE scores to gauge the ideological location of major political figures and institutions in his FiveThirtyEight Blog.

NOMINATE procedures and related roll call scaling techniques have also been applied to a number of other legislative bodies besides the United States Congress

United States Congress

The United States Congress is the bicameral legislature of the federal government of the United States, consisting of the Senate and the House of Representatives. The Congress meets in the United States Capitol in Washington, D.C....

. These include the United Nations General Assembly

United Nations General Assembly

For two articles dealing with membership in the General Assembly, see:* General Assembly members* General Assembly observersThe United Nations General Assembly is one of the five principal organs of the United Nations and the only one in which all member nations have equal representation...

, the European Parliament

European Parliament

The European Parliament is the directly elected parliamentary institution of the European Union . Together with the Council of the European Union and the Commission, it exercises the legislative function of the EU and it has been described as one of the most powerful legislatures in the world...

National Assemblies in Latin America

Latin America

Latin America is a region of the Americas where Romance languages – particularly Spanish and Portuguese, and variably French – are primarily spoken. Latin America has an area of approximately 21,069,500 km² , almost 3.9% of the Earth's surface or 14.1% of its land surface area...

, and the French Fourth Republic

French Fourth Republic

The French Fourth Republic was the republican government of France between 1946 and 1958, governed by the fourth republican constitution. It was in many ways a revival of the Third Republic, which was in place before World War II, and suffered many of the same problems...

. Poole and Rosenthal note in Chapter 11 of Ideology and Congress that most of these analyses produce the finding that roll call voting is organized by only few dimensions (usually two): "These findings suggest that the need to form parliamentary majorities limits dimensionality."

External links

The source of this article is wikipedia, the free encyclopedia. The text of this article is licensed under the GFDL.