13 Political science measures

13.1 GDP

GDP refers to the gross domestic product, which is a measure of the dollar value of goods and services produced in a particular location within a particular time. For example, the GDP of the United States in 2024 was about $29 trillion, which means that about $29 trillion of market value goods and services were produced in the United States in 2024.

GDP can be used to measure the economic performance of one country relative to another country, but a few important caveats are:

  1. GDP doesn’t account for non-market activity. For example, if a parent cares for their child eight hours per day, that does not contribute to GDP. But if a parent pays a nanny $100 to care for the child eight hours per day and the parent makes $200 per day, GDP has increased by $300.

  2. GDP is larger, all else equal, with a larger population. To address this, we can use a measure called GDP per capita, which is GDP divided by population.

  3. GDP can rise merely through inflation. To address this, we can use a measure called real GDP, which accounts for inflation by adjusting dollar values to reflect a base year. On the other hand, nominal GDP is not adjusted for inflation.

  4. GDP can be adjusted to reflect local prices. Purchasing Power Parity (PPP) adjusts GDP so that the same GDP can purchase the same basket of goods and services in each side of a comparison.

Does GDP account for non-market activity?

  1. Yes
  2. No
Answer
  1. No

Which of the following is defined as GDP adjusted for inflation?

  1. GDP per capita
  2. Real GDP
  3. Nominal GDP
  4. Purchasing Power Parity
Answer
  1. Real GDP

Which of the following is adjusted to reflect local prices?

  1. GDP per capita
  2. Real GDP
  3. Nominal GDP
  4. Purchasing Power Parity
Answer
  1. Purchasing Power Parity

13.2 Gini coefficient

The Gini coefficient measures inequality. This is often uses to measure income inequality, in which 0 indicates that everyone member of the population has the same income and 1 indicates that one person has all of the income.

The Gini coefficient measures…

  1. economic activity
  2. inequality
  3. inflation
  4. unemployment
Answer
  1. inequality

13.3 Ideology scores among elites

A political party is an association of persons who tend to agree on basic goals of government. There are two major political parties in the United States: the Democratic Party, and the Republican Party. There are also political ideologies in the United States that reflect fundamental beliefs about government. For the most part, for these political ideologies, people can be aligned from the political left (liberal) side to the political right (conservative side). Democrats tend to be on the political left, and Republicans tend to be on the political right.

IDEOLOGY: Liberal  ...   Moderate   ... Conservative
PARTY:    Democrat ... Independent  ... Republican

In the United States, which party below is the more conservative party?

  1. the Democratic Party
  2. the Republican Party
Answer
  1. inequality

Suppose that we wanted to measure the political ideology of each U.S. Supreme Court justice. One method that political scientists have used has been to calculate the percentage of cases in which the justice voted conservatively, so that justices can range from 0 for very liberal (voting conservatively in 0% of cases) to 100 (voting conservatively in 100% of cases). But a flaw with this measure is that a researcher must decide for each case which direction is the conservative direction, and sometimes cases do not clearly map onto left/right ideology, such as if the case is non-ideological or if the case touches on questions that balance different ideologies; for example, if a court rules in favor of gun rights for immigrants, should that be coded as a conservative decision (focusing on gun rights) or a liberal decision (focusing on the rights of immigrants)?

Martin-Quinn scores instead essentially (to simplify things a lot) reflect how frequently the justices vote together in a case. If two justices always vote together, then those justices will have the same ideology score. But the more often these two justices vote differently from each other, the farther apart their scores will be from each other. A nice feature of these Martin-Quinn scores is that a researcher does not need to decide which direction in each case is the conservative direction. This method will tend to give each justice a different number. This method won’t tell us whether the higher numbers are more liberal or more conservative, but we can figure it out when we see Ruth Bader Ginsburg and Sonia Sotomayor with negative scores and Clarence Thomas and Samuel Alito with positive scores.

Below are scores for the U.S. Supreme Court in the 2023 term, which ran from Monday October 2, 2023 to Sunday October 6, 2024:

Sotomayor -4.09
   Kagan -2.46
     Jackson -2.05
        Roberts 0.51
           Kavanaugh 0.52
              Barrett 0.69
                 Alito  2.53
                    Thomas 3.09

Martin-Quinn scores are great within a particular term of the U.S. Supreme Court and over short periods of time, but Martin-Quinn scores aren’t necessarily great over long periods of time, for addressing whether (for instance) the U.S. Supreme Court has gotten more liberal or more conservative over the past few decades.

But Michael Bailey has a method to addresses this, by using bridging observations. The logic goes like this: in 1973, the justices on the U.S. Supreme Court decided Roe v. Wade, which interpreted the U.S. Constitution to protect a woman’s right to an abortion in certain circumstances. Over the years, later justices commented about whether Roe v. Wade was decided correctly, and in 2022 the U.S. Supreme Court overturned what had survived of the Roe ruling. Therefore, we can treat the later justices who supported the Roe ruling and who voted to uphold Roe as if they had the same judicial ideology on this question as the justices who voted in 1973 in favor of the Roe decision. And we treat the later justices who spoke against the Roe decision and who voted to overturn Roe as if they had the same judicial ideology on this question as the justices who voted in 1973 against the Roe decision. Bailey has identified a lot of these bridging cases to help compare justices over time.

Bailey’s method also permits legislators and presidents to be placed on the same scale, given that legislators and presidents also have expressed opinions about U.S. Supreme Court decisions. And, in addition to court cases, Bailey also uses other types of “bridges”, such as a presidential veto or a presidential signing of bills that some legislators voted for and that other legislators voted against.

Martin-Quinn scores are similar to DW-NOMINATE scores, which were developed by Keith T. Poole and Howard Rosenthal earlier than Martin-Quinn scores. These DW-Nominate scores are based on voting agreement among legislators in the U.S. Congress. An interesting element of DW-NOMINATE scores is that sometimes the scores have an important second dimension. The first dimension is the left/right liberal/conservative dimension, but (for example) during the mid-1900s, votes on civil rights / racial issues did not correlate with other political issues as highly as they correlate with other political issues today. Nowadays, if you know that a U.S. legislator is a Democrat who is economically liberal, that U.S. legislator is almost certainly also liberal on racial issues. But we couldn’t be as certain about that correlation in the 1950s and 1960s.

Measures of elite ideology such as DW-Nominate scores and Martin-Quinn scores are constructed based on…

  1. expert judgments
  2. percentage of times elites vote in a conservative or liberal direction
  3. public opinion polls
  4. surveys of the elites
  5. voting agreement among elites
Answer
  1. voting agreement among elites

For DW-Nominate scores and Martin-Quinn scores, lower scores indicate what type of ideology?

  1. conservative
  2. liberal
Answer
  1. liberal

In the mid-1900s, DW-Nominate scores had a meaningfully important second dimension that captured disputes about…

  1. civil rights policy
  2. tax policy
  3. U.S. entry in World War II
Answer
  1. civil rights policy

13.4 Polity scores

Polity scores measure regime type, on a scale from -10 for strongly autocratic (dictatorship) to +10 for strongly democratic. These Polity scores are from the Center for Systemic Peace and are based on expert judgments about a set of criteria. Experts judgments are used to construct a autocracy score and a democracy score, and these scores are combined into the Polity measure of regime type.

From the codebook, with emphasis added:

Democracy is conceived as three essential, interdependent elements. One is the presence of institutions and procedures through which citizens can express effective preferences about alternative policies and leaders. Second is the existence of institutionalized constraints on the exercise of power by the executive. Third is the guarantee of civil liberties to all citizens in their daily lives and in acts of political participation. Other aspects of plural democracy, such as the rule of law, systems of checks and balances, freedom of the press, and so on are means to, or specific manifestations of, these general principles. We do not include coded data on civil liberties.

For an example of these criteria:

  • If the chief executive has unlimited power, that adds +4 to the country’s autocracy score

  • If the chief executive is subject to slight-to-moderate limitations, that adds +1 to the country’s autocracy score

  • If the the chief executive is subject to substantial limitations, that adds +2 to the country’s democracy score

  • If the chief executive has parity or is subordinate, that adds +4 to the country’s democracy score

Polity measures of regime type are constructed based on…

  1. expert judgments
  2. surveys of world leaders
  3. World Bank data
Answer
  1. expert judgments

Based on the Polity criteria, which of these is not an essential element of democracy?

  1. civil liberties for the citizens
  2. constraints on the executive
  3. mechanisms by which citizens can express effective preferences about their leaders
  4. term limits on elected leaders
Answer
  1. term limits on elected leaders

13.5 Racial resentment

See if you can figure out which response – agree or disagree – is the more “racially resentful” response to each of the four statements below:

  • Irish, Italians, Jewish and many other minorities overcame prejudice and worked their way up. Blacks should do the same without any special favors.

  • Generations of slavery and discrimination have created conditions that make it difficult for blacks to work their way out of the lower class.

  • Over the past few years, blacks have gotten less than they deserve.

  • It’s really a matter of some people not trying hard enough; if blacks would only try harder they could be just as well off as whites.