Methodology

June 2018

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The 2018 VOTER Survey (Views of the Electorate Research Survey) was conducted by the survey firm YouGov. In total, 6,005 adults (ages 18 and up) with internet access took the survey online between April 5 and May 14, 2018. The reported margin of error is plus or minus 2 percent.

Of this group, 4,705 respondents are long-term participants (“panelists”) in the VOTER Survey, 500 respondents comprise a new over-sample of Hispanics, and 800 respondents comprise a new over-sample of voters ages 18 to 24 (who were too young to be interviewed in the earliest survey).

The earlier waves of the VOTER Survey proceeded as follows: Panelists were first interviewed by YouGov in 2011-2012 as part of the 2012 Cooperative Campaign Analysis Project (CCAP). In that survey, 45,000 respondents were first interviewed in December 2011 and were interviewed a second time in one of the 45 weekly surveys between January 1 and November 8, 2012. After the 2012 election, 35,408 respondents were interviewed a third time. In December 2016, 11,168 panelists from 2012 CCAP were invited to respond and 8,637 of them (77 percent) completed the survey. YouGov also supplied measures of primary voting behavior from the end of the primary period (July 2016), when these respondents had been contacted as part of a different survey project. This December 2016 survey (N=8,000) constitutes the first VOTER Survey. The second survey, in July 2017, was the second VOTER Survey (N=5000). This May 2018 survey is thus the third VOTER Survey.

The table below shows how many respondents were interviewed in various combinations of these surveys. Shaded areas indicate a completed interview:

The 2012 CCAP was constructed using YouGov’s sample matching procedure. A stratified sample is drawn from YouGov’s panel, which consists of people who have agreed to take occasional surveys. The strata are defined by the combination of age, gender, race, and education, and each stratum is sampled in proportion to its size in the U.S. population. Then, each element of this sample is matched to a synthetic sampling frame that is constructed from the U.S. Census Bureau’s American Community Survey, the Current Population Survey Voting and Registration Supplement, and other databases. The matching procedure finds the observation in the sample from YouGov’s panel that most closely matches each observation in the synthetic sampling frame on a set of demographic characteristics. The resulting sample is then weighted by a set of demographic and non-demographic variables (in the data set, this is the variable “weight”).

On average, YouGov’s methodology produces less bias across a series of benchmarks than do other methodologies using online samples. For more information on the process see:

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