November 2, 2016

Just how does the general election exit poll work, anyway?

Terry and Mary Ann Williams fill out exit polls conducted by Edison Research after voting at the Bayleaf Volunteer Fire Department on November 6, 2012 in Raleigh, North Carolina. Photo by Sara D. Davis/Getty Images
Terry and Mary Ann Williams fill out exit polls conducted by Edison Research after voting at the Bayleaf Volunteer Fire Department on Nov. 6, 2012, in Raleigh, North Carolina. (Photo: Sara D. Davis/Getty Images)

As millions of Americans watch election results roll in on Tuesday, they’ll learn a lot more than whether Hillary Clinton or Donald Trump will become the 45th president. They’ll be told such things as how college-educated Republican women in Florida voted, what issues drove voters to the polls in Ohio, and how many of Utah’s Mormons cast their ballots for independent candidate Evan McMullin.

The source for those sorts of detailed analyses of the electorate is Edison Research. The Somerville, New Jersey-based firm has conducted exit polls for the National Election Pool (a consortium of ABC, CBS, NBC, CNN, Fox and The Associated Press) since 2003 – originally in conjunction with Mitofsky International, and since 2006 on its own. But just how does Edison do it?

Joe Lenski, Edison’s co-founder and executive vice president, said the firm will interview voters as they leave the polls at nearly 1,000 locations (a random stratified probability sample of the more than 110,000 physical polling places across the country). And since Edison expects between 35% and 40% of the vote to be cast before Election Day, it also is conducting a phone survey of early and absentee/mail voters, a process that began earlier this week. 

Joe Lenski, co-founder and executive vice president of Edison Research
Joe Lenski, co-founder and executive vice president of Edison Research

The exit poll is a major operation. Edison expects to survey about 16,000 early and absentee voters by phone, Lenski said, and another 85,000 or so voters in person. “Between exit-poll interviewers, vote-count reporters, supervisors driving around checking on sites, and the two very large phone rooms we’ll be operating on Election Day to take in those results, we have close to 3,000 people working for us on Election Day,” he said.

The exit poll is more a set of interlocking surveys than a single, uniform poll. Aside from the phone and in-person components, Edison will field state-specific questionnaires at 350 of its 1,000 or so polling locations, in addition to the national questionnaire all respondents receive. The idea, Lenski said, is to be able to ask about issues that might be particularly relevant in key states.

“In Utah, for example, which has a large Mormon population, we’ll have questions specific to that population,” he said. “And you’ll see bigger state sample sizes in the big battleground states like Florida and Ohio.”

Rather than conducting oral interviews at polling places, Edison gives respondents written questionnaires to fill out. There are a couple of reasons for that, according to Lenski.

“One, we try to make the experience of registering your vote on the exit poll as close as we can to registering your vote at the polling place,” he said. “The other reason is that we don’t want to interfere with the election process, and asking people who they voted for as they’re leaving the polling place could be overheard by people going in. One of the reasons we get cooperation from election officials is that we can confirm that those questionnaires are private and confidential. There’s no notation on the questionnaire as to who filled it out.”

Edison’s response rate on its exit polls is considerably higher than is typical for phone surveys, Lenski said – about 45% of the voters the firm approaches agree to fill out questionnaires. But, he added, “Response rates in exit polls have gone down, but a lot more gradually than with traditional telephone surveys. When I started in this business, the response rate was more like 60%.”

That being the case, Edison’s field researchers try to address nonresponse bias – that is, the risk that the firm’s sample may not be representative of the entire electorate because of who chooses not to participate.

“Since we are at the polling place, our interviewers can record some characteristics of voters who decline to take part in the survey – approximate age, gender and race – so we can adjust our results for those factors,” Lenski said. “But there are other items we can’t account for visually. People don’t have a D or an R stamped on their foreheads, and you don’t know as they walk past you whether or not they have a college degree.”

After the polls close and actual results begin to be released, Edison will factor them in. If the returns differ markedly from the exit-poll results, the firm will update its analyses and projections accordingly.

“We will know shortly after the polls close,” Lenski said. “We’ll have individual precinct results from all the locations where we conducted interviews, so we’ll know how much understatement or overstatement for the candidates we have. Our calls are based on all the information we have at the time – exit polls, returns from sample precincts and county results from AP – and we may re-weight the exit poll results later in the evening to match the vote estimates by geographic region.”

The exit poll, he said, “is the one survey out there where you get evaluated immediately. We’ll process over 100,000 interviews, and within two hours we know how well we did.”

As early and absentee voting and vote-by-mail have become ever more significant, Lenski said, he’s also learned how those alternatives differ from each other.

“Historically, by which I mean before 2000, early voting was almost entirely absentee by mail, and it tended to be older voters,” he said. “Since the 2000 election, the Democratic Party has put a great deal of emphasis on early in-person voting, especially in states like Florida. It varies from state to state, depending a lot on the history in those states and how the political parties in in those states approach early voting, [but] the in-person early voting tends to be encouraged more by voter outreach and to be more Democratic, and the absentee by mail tends to be older voters or people who are traveling out of state, and to be more Republican.”

Colorado, Oregon and Washington are the only three states that conduct their elections entirely by mail, and Lenski has noticed trends based on when ballots are turned in.

“The pattern has been that the later-returned ballots in those states tend to be more Democratic and the ones turned in earlier tend to be more Republican,” he said. “One other thing we’ve seen sometimes is that the ballots turned in earlier tend to get counted first on Election Day, so that’s something we have to consider when we’re making our projections.”

“It definitely adds a source for more potential bias or error,” he added. “If Colorado or Arizona, for instance, looks like it might be a close state, we might be a lot more cautious about calling it until more actual votes are released.” (In Arizona, a normally Republican state where polls show a close race this year, two-thirds of the total 2012 vote was cast absentee.)

Besides the general-election exit poll, Edison also conducted exit polls during the Democratic and Republican primaries and does similar work in other countries. Overall, Lenski said, only 40% of Edison’s work is election-related. The firm’s main business is consumer research, tracking everything from what songs radio listeners prefer to which types of ads are most and least effective.

But the presidential exit poll is Edison’s highest-profile project, and the one that’s hardest to pull off successfully. In fact, Lenski said, the firm starts the process of picking its sample precincts more than a year before Election Day.

“A typical Election Day for me starts a little before 6 a.m., and I’m usually up for about 36 straight hours,” he said. “Hopefully I’ll have time on Wednesday to collapse and catch up on two days’ worth of sleep.”

Topics: Research Methods, Voter Participation, Polling, 2016 Election

  1. Photo of Drew DeSilver

    is a senior writer at Pew Research Center.


  1. Anonymous9 months ago

    I wish there were no (zero) polling, both before and after voting takes place. What is the purpose of conducting polls? Voters should decide on their own and not be influenced by polling data.

    1. Brian Spoelhof9 months ago

      There are countless reasons polls exist.
      First, and most importantly, exit polling provides a cross reference to how people voted. Example, if exit polls show candidate A was winning against candidate B 51% to 49%, but candidate B wins, there is a major problem. Either people lied about who they just voted for, or there was voter fraud. In fact, exit polls are the most reliable method to detect fraud.
      Second, did you know there was over 30 republican candidates running during the primaries? How did they determine who would go to the debates? Polls. Sure, you could let anyone go on stage and debate, but that could mean 100s or 1000s of people would be on the stage. Instead, candidates had to have a certain percentages in the polls to appear.
      Third, polls actually protect the people’s voice. Let’s take the example above regarding the debates. The candidates that appear are ones people “voted” for in the polls. We already agree everyone can’t go on stage. So who gets to choose who is allowed to debate. The parties? Rich people? Big Business? Those already in power? Essentially anyone BUT the people.
      Finally, as I said before, polls protect your voice. When voters say that the economy is most important to them, or social injustice, or taxes – They are essential dictating the areas of policy candidates will work on.

      There are so many other reasons polls provide benefits and it is truly unfortunate that people are so misinformed and uneducated that there is an automatic assumption of malice. You could argue that poll data could be kept secret so they don’t influence the election. However, do you really want them to hide that information from the public, do you want lack of transparency?

      1. Anonymous9 months ago

        It was an interesting article. Perhaps I should have known this, but the poll process is highly dependent on what people write down, and has no quantitative basis. I’ll explain: PEW gathers information, which we will assume is flawed at its source. Then, it fine tunes its results as it gets qualitative results from an actual ( fact based) vote count. At the end, the poll is assured to reflect the actual. There is little as in “none” statistical inference the poll at any stage before the election is based in fact or evidence.

        This election, as perhaps others, confirms the POLL is a guess based on unverifiable information. I took your survey, and I lied. That your team “views” people and makes educated guesses on race, age is equally flawed given we are a blended America.

        Given all of the companies in America which can link names to drivers licenses, to IDs, and give an accurate picture of America, it is a disappointment Pew Research depends on information which can be flawed at its source. Lesson learned, I guess. Funny also the “big networks” originally funded this single myopic view of its paper based polls.

        Equally, one “could” influence the polls, and the primaries, by favoring (on paper) one candidate vs the other. As a person who lives and develops statistical inference, I find Pew’s process flawed, as the election in 2016 demonstrates it was wrong. (And don’t get me started it was flawed within the margin of error, it is just flawed, and no better than a guess.)

        A well written article, very surprised still, it is based on unverifiable exit polls. But thank you for sharing.

  2. William H. Magill10 months ago

    Very interesting article. Exit Polling is one thing you hear about, but nobody has ever described what actually happens.

    With all of the various comments about how people are not telling pollsters what they really think, we will see if this year their methodology still works.

  3. Anonymous10 months ago

    I wish they would ban the practice of exit polling. It does nothing other than influence the election.

    1. Anonymous10 months ago

      Not sure about that. It allows for a lot of detailed analysis after the election as well. Would voters be swayed by exit polls? If so they weren’t very committed to their candidate.

    2. Anonymous9 months ago

      It would seem you are correct. It (Exit Polls) isn’t based on fact, and is unverifiable. We should eliminate the exit polls unless they can be verified. Instead, we should focus real resources on how we would allow a Sweedish person, Wikileaks, and perhaps (unverified) the Russians, from using trickle down news (also unverified) to influence out voting process.

    3. Anonymous9 months ago

      A person does (or refuses to do) an _exit_ poll _after_ they vote, not before they vote. So that process does not influence any election. The exit poll results are not leaked during election day, so collecting results does not influence the election.
      Maybe your complaint is about networks broadcasting the East Coast partial vote before West Coast voting is complete. Right – they should wait till midnight for HI.

      A much more serious problem is that many network “news shows” now present biased opinion as if it were fact. They let guests say untrue & misleading statements, with no comment about their falseness. They pay their anchors to spread rumor and gossip, so long as the network thinks their viewers want to hear it. This is NOT NEWS.

      “News Shows” have become worthless in the 30 years since Reagan trashed the Fairness Doctrine.