Opinión Pública y Análisis de Encuestas

David Crow, Associate DirectorUC Riverside, Survey Research Center

david.crow@ucr.edu

Módulo VII: Encuestas y eleccionesviernes 8 de julio de 2010

Polls and Elections(Asher, Chap. 7)

• Types of Polls- Who sponsors survey?- What is survey used for?

• Campaigns Use of Polls to Influence Voters- Jumping on the bandwagon?

• Media Coverage of Campaigns– Off to the races horse race instead of substantive coverage

• Why Polls Go Wrong

• Effects of Polls on Elections

Types of Polls: Benchmark• Benchmark Surveys: Initial poll to assess candidate

viability; serves as baseline against which to measure progress

Asks about1) Name recognition2) Electoral strength vis-à-vis opponent3) Support for Incumbent

Problems: typically done very early into a campaign, so - people are unlikely to know much about the challenger- economic and political circumstances could change

Typically only leaked if they show a candidate doing well

Types of Polls: Trial Heat• Trial Heat Questions: Series of questions in a survey

that pair candidates in hypothetical races E.g., “If elections were held today, would you vote for A or B?”

Problems: 1) Abet “horse race” focus of media coverage2) Changing circumstances between survey and election day3) Is it a measure of candidate or party appeal? Not clear in

case of lesser-known candidates4) Also, leaves out relevant alternatives three two-way

races (between A and B, B and C, and A and C) not the same as one three-way race

5) Pairs chosen have “framing effect” on race

Types of Polls: Tracking Poll• Tracking Poll: Polls undertaken on a daily basis close

to election day goal is to monitor trends (rises and falls) in support for candidates

- Rolling sample: New sample chosen every day, so tendency reported is a “moving average” over several days “smoothes out” random fluctuation

Problems: - extraordinary events could swing preferences wildly for

one day, throwing off average over several days- Sometimes volatile in their predictions small samples

could lead to wild fluctuations in, e.g., distribution of party preferences

Types of Polls: Focus Groups• Focus Group: in-depth interviews with small group of

people chosen to represent broad demographic groups (e.g., “soccer moms”)

Used for 1) debate preparation; 2) political marketing; 3) survey item development; 4) gauge public sentiment on issues e.g., 1992 Willie Horton ad

Problems: although they can be a valuable tool, media often fail to recognize methodological limits not representative; “groupthink” people’s opinions may be different in a group setting than in isolation

Types of Polls: Exit Polls• Exit Poll: Interviews of voters as they leave the

polling place; advantage: we know people actually voted

Problems: - Don’t take into account absentee ballots- Non-response bias some groups more willing to

participate than others- Social desirability- Do poll results in Eastern states affect outcomes, turnout in

the West? 1980 presidential election

Types of Polls: “Push” Polls

• Push Poll: Tendentious questions that feed misleading or false information to voters in an attempt to sway vote against a candidate

Propaganda disguised as scientific research

Protecting against “push polls”: 1) ask for name of organization conducting poll; 2) length of survey greater for legitimate polls; 3) number of calls far higher in a push poll

How Candidates Use Polls• Gauge the viability of a candidacy: commission private poll; bad news

might dissuade a candidate from running

• Get Campaign Donations: news releases of good results as proof of viability, possibility of winning

• Bad Results?: cast aspersion on credibility of polls; three common responses: 1) too early to tell; 2) attack pollsters and journalists; 3) counter the results with other polls. Also, question methodology

• Manipulate Polls to Promote Candidacy: – Selectively leak results– Tweak survey design to get desired results

» “priming” voters to evaluate candidates on favorable traits» Sample selection» Supplying negative information on opponent

Polls and Presidential Selection• Ubiquity of polls in all phases of presidential

campaigns statewide polls in primary states, national polls, etc.

– Pollsters become part of campaign team– Strategy based on (or takes into account) poll results

• Do polls reflect current state of public opinion, or do they sway vote choice?

- Reporting polls results creates “momentum”, and feedback cycles- Affect fund-raising abilities

Polls and Presidential Elections• Instant Polls: instantaneous or overnight polls media’s

focus on immediate reaction decreases quality of polling– Proportional to number of days in field– Proportional to number of respondents– Interviews only people available at a certain time

• Polls as Filters: third-party and lesser-known candidates can’t become known, because they can’t reach threshold (15% in 1980, as set by LWV) of vote preferences to participate or are excluded outright; case of Ross Perot in 1992

– Other standards: national organization, newsworthiness, enthusiasm for candidacies (as demonstrated by polls)

– BUT, should just anyone who wants to participate be able to? Debates should not be cluttered with frivolous candidates who sets and enforces standards? Bipartisan commission is exclusive

Media Reporting of Polls• Overemphasis on poll results

• Undue magnification of small shifts in preferences these are random fluctuations, new true changes in preferences

• Subtleties of poll methodology go unreported

• Media focus on own polls, ignore other pollsters averages over polls are more accurate than any individual poll

Polls’ Effects on Voters• Do polls mobilize or demobilize voters?

- “Bandwagon” effect: Polls rally voters behind candidate in lead, discourage people from voting for trailing candidates

- “Underdog effect”: voters rally behind candidate who is behind• Evidence:

- Experimental designs: poll preferences, expose voters to other poll results, take poll afterwards inconclusive: de Bock (1976) found evidence of discouragement, Marsh (1984), of underdog effect

- Survey questions: ask voters about their exposure to polls, and directly whether polls influence choice; problems imperfect recall and people unwilling to admit they are influenced by polls

• Polls can also have indirect effects influence campaign contributions, media coverage, other attitudes

¡A veces se equivocan las encuestas electorales!

Polls Are Sometimes Wrong!• Most Are Pretty Accurate: however, some notorious

mistakes (and run-of-the-mill problems)- Literary Digest 1936 incident self-selected sample predicted

Alf Landon (who?) victory over FDR- 1948 Dewey vs. Truman quota sampling method (not

probability) and premature cut-off to polling predicted Dewey victory, despite narrow lead (5%) and downward trend

- 1980 Reagan victory predicted tight race instead of 10% Reagan landslide; polling failed to pick up last-minute surge in Reagan support among undecideds

- 1992 general election conflicting poll results; criticism over sampling, allocation of undecideds to candidates, shift from “registered” to “likely” voters

- 1996 Clinton victory: overestimated margin of victory, widely varying polls for House

Why Polls Are Wrong: Timing• The closer a poll is to the election, the more likely it is to be right

– Later polls capture effects of last-minute events and campaign activities Crespi (1988) found this was most important factor, followed by margin of victory (wider margin more accurate polls) and turnout (higher turnout more accurate)

– Earlier polls are likelier to reflect name recognition of candidates

• Polls do better when they 1) do well at identifying likely voters and 2) track voter preferences over time

• E.g., Bush Sr.’s win in New Hampshire primaries: – Most polls stopped too early– Tracking polls (CBS) did better at predicted margin of victory

• Media focus on own polls, ignore other pollsters averages over polls are more accurate than any individual poll

Why Polls Are Wrong: Undecideds• Three reasons for “undecided” response

– Voters genuinely cannot make up minds lack of information– Unwilling to make choice– Unwilling to reveal choice to pollster

• Polls that do not account for undecideds may not yield best predictions

– E.g., Wilder race in Virginia (“Wilder effect”) and Dinkins in NY: “undecided” masked race effects in which whites who intended to vote for white candidate (or were talking with black interviewer) said they were “undecided”

• Methods for dealing with “undecided” problem:– “Secret ballot” method pioneered by Gallup: simulates real election by giving voters

ballot; interviewer does not see choice (only used with face-to-face)– Ignore undecideds and tabulate results only for those who state a preference problem:

some will vote, and they may differ in their choices than those with stated preferences– Allocate undecideds in proportion to preferences not good when one candidate is more

well known than others– Allocate undecideds on other factors, such as party ID, sociodem.

Why Polls Are Wrong: Turnout• Likely Voter Problem: which respondents will really vote? “Social

Desirability” overestimates probability of voting; Problem preferences of voters and non-voters are probably different

• Methods for assessing likely voters:– Self-reported intention to vote– Registration status– Reported frequency of past voting– Knows where polling site is– Interest in politics– Interest/awareness of campaign– Intensity of candidate preferences

• Estimates can be based on only those classified as “likely voters”, or weighted by predicted probability of voting

• Different polling agencies use different combinations of these factors

Why Polls Are Wrong: Changing Economic and Political Environment

• Changing circumstances (economic crisis, campaign intensity, scandal) could motivate some citizens to vote that might other

• E.g., 1982 midterm election: polls underestimated Democratic turnout motivated by economic recession labor unions, ethnic advocacy groups had effective get-out-the-vote (GOTV) operations

• E.g., 1994 midterm: Republican “Contract with America” polls underestimated Republican victory; Clinton campaigns had reverse effect of mobilizing Republicans

Pronósticos electorales y votantes probables

• Una de las metas más sonadas de las encuestas preelectorales es la de pronosticar el resultado electoral.

• Sin embargo, ello se complica porque se les entrevista no a quienes van a voter, sino a adultos en edad de votar

• Es decir, hay una especie de error de cobertura, porque el marco muestral incluye a personas que no forman parte de la población

¿Cómo determinar los votantes probables?Probabilidad autorreportada de votar

• Preguntar directamente sobre la intención de votar.• La pregunta típica es “Qué tan probable es que Ud. vaya a votar en la

próxima elección?”• Definitivamente• Muy probable• Algo probable• Poco probable• Nada probable

• 1) se sustrae de la base de datos quienes contestaron de “muy probable” para abajo, p.e., y la pregunta de intención de voto se hace sólo sobre quienes dijeron “definitivamente” O

• 2) se asignan valores numéricos (arbitrarios o con base en encuestas previas) a las probabilidades y se realiza una ponderación con base en esas probabilidades

¿Cómo determinar los votantes probables?Participación electoral previo

• Se pregunta sobre si el entrevistado votó en la elección pasada (o las elecciones pasadas)

• Distintos tipos de elecciones: federales, estatales, municipales, etc.

• Se le asigna una mayor ponderación a quienes votaron—nuevamente, de forma arbitraria o basándose en información externa (encuestas poselectorales, verificación del voto, etc.)

¿Cómo determinar los votantes probables?Actitudes hacia la política

• Se pregunta sobre: • Interés por la política• La atención ha puesto en la campaña electoral, • Si platica de política con otra gente• Otro tipo de actividades políticas (participar en campañas,

contactar a sus diputados, etc.)

• Pregunta típica: “¿Qué tanto se interesa Ud. por la política?”• Muy• Algo• Poco• Nada

El método de Gallup• Siete preguntas, seis relacionadas con historia de participación

electoral y una sobre “qué tanto ha pensado en la próxima elección”

• Se asigna un punto a cada pregunta para sacar una escala de 0 a 7.

• Basándose en estudios internos de “validación del voto” (en los que personal de Gallup va a los registros locales electorales para cerciorarse de que la gente que dijo que iba a votar, votó—pues la participación electoral es información pública en EE.UU—), se determinó que quienes tenían un puntaje de 7 en la escala, contaban con una probabilidad de votar del 55% porciento.

• Se pondera la muestra por esas probabilidades.

Otros métodos de evaluar la probabilidad de votar:

• Otras encuestas:• Calcular la probabilidad de votar de encuestas poselectorales usando regresión

logística multivariada• Usar esas probabilidades para calcular ponderadores• Aplicar los ponderadores a una encuesta preelectoral

• Ponderar con información de la población:• El problema de votantes probables es uno de no respuesta diferencial quienes

no van a votar contestan la encuesta en proporción mayor a quienes sí van a votar

• Se puede posestratificar una encuesta preelectoral• Definir estratos como edad, sexo, raza, estado, etc.• Usar información del censo (u otra fuente) para saber las proporciones de esas

variables en la población• Ajustar las proporciones de la muestra a las de la población

Cuadro comparativo de correcciones para votantes probables

Candidate IFE CD CD w/ Likely

Voter

MPS MPS w/ Likely

Voter + Weights

MPS w/ Likely

Voter + ID

MPS w/ Interest

+ Weights

FCH 36.7% 29.4% 29.2% 31.4% 36.7% 34.0% 35.3%

AMLO 36.1% 27.4% 31.3% 37.1% 33.4% 37.6% 35.6%

RMP 22.7% 27.02% 25.8% 26.2% 24.9% 27.4% 26.7%

CD = Citizen Disenchantment (June, 2006, N=509)CD Likely Voter = only those who said they would “definitely” voteMPS = Mexico 2006 Panel Study (May, 2006, N=1,914)MPS Likely Voter = only those who said they were “totally sure” they would voteMPS ID = only those who had a valid voter IDMPS Interest Weights = 2 for “a lot” of interest, 1.33 for “some”, 0.67 for “a little” and 0 for none