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Ten Reasons Why You Should Ignore Exit Polls:
From FiveThirtyEight:
1. Exit polls have a much larger intrinsic margin for error than regular polls. This is because of what are known as cluster sampling techniques. Exit polls are not conducted at all precincts, but only at some fraction thereof. Although these precincts are selected at random and are supposed to be reflective of their states as a whole, this introduces another opportunity for error to occur (say, for instance, that a particular precinct has been canvassed especially heavily by one of the campaigns). This makes the margins for error somewhere between 50-90% higher than they would be for comparable telephone surveys.

2. Exit polls have consistently overstated the Democratic share of the vote. Many of you will recall this happening in 2004, when leaked exit polls suggested that John Kerry would have a much better day than he actually had. But this phenomenon was hardly unique to 2004. In 2000, for instance, exit polls had Al Gore winning states like Alabama and Georgia (!). If you go back and watch The War Room, you'll find George Stephanopolous and James Carville gloating over exit polls showing Bill Clinton winning states like Indiana and Texas, which of course he did not win.

3. Exit polls were particularly bad in this year's primaries. They overstated Barack Obama's performance by an average of about 7 points.

4. Exit polls challenge the definition of a random sample. Although the exit polls have theoretically established procedures to collect a random sample -- essentially, having the interviewer approach every nth person who leaves the polling place -- in practice this is hard to execute at a busy polling place, particularly when the pollster may be standing many yards away from the polling place itself because of electioneering laws.

5. Democrats may be more likely to participate in exit polls. Related to items #1 and #4 above, Scott Rasmussen has found that Democrats supporters are more likely to agree to participate in exit polls, probably because they are more enthusiastic about this election.

6. Exit polls may have problems calibrating results from early voting. Contrary to the conventional wisdom, exit polls will attempt account for people who voted before election day in most (although not all) states by means of a random telephone sample of such voters. However, this requires the polling firms to guess at the ratio of early voters to regular ones, and sometimes they do not guess correctly. In Florida in 2000, for instance, there was a significant underestimation of the absentee vote, which that year was a substantially Republican vote, leading to an overestimation of Al Gore's share of the vote, and contributing to the infamous miscall of the state.

7. Exit polls may also miss late voters. By "late" voters I mean persons who come to their polling place in the last couple of hours of the day, after the exit polls are out of the field. Although there is no clear consensus about which types of voters tend to vote later rather than earlier, this adds another way in which the sample may be nonrandom, particularly in precincts with long lines or extended voting hours.

8. "Leaked" exit poll results may not be the genuine article. Sometimes, sources like Matt Drudge and Jim Geraghty have gotten their hands on the actual exit polls collected by the network pools. At other times, they may be reporting data from "first-wave" exit polls, which contain extremely small sample sizes and are not calibrated for their demographics. And at other places on the Internet (though likely not from Gergahty and Drudge, who actually have reasonably good track records), you may see numbers that are completely fabricated.

9. A high-turnout election may make demographic weighting difficult. Just as regular, telephone polls are having difficulty this cycle estimating turnout demographics -- will younger voters and minorities show up in greater numbers? -- the same challenges await exit pollsters. Remember, an exit poll is not a definitive record of what happened at the polling place; it is at best a random sampling.

10. You'll know the actual results soon enough anyway. Have patience, my friends, and consider yourselves lucky: in France, it is illegal to conduct a poll of any kind within 48 hours of the election. But exit polls are really more trouble than they're worth, at least as a predictive tool. An independent panel created by CNN in the wake of the Florida disaster in 2000 recommended that the network completely ignore exit polls when calling particular states. I suggest that you do the same.

Related Posts (on one page):

  1. Extreme Measures:
  2. Ten Reasons Why You Should Ignore Exit Polls:
  3. Exit Polls:
Displaced Avenger:
I thought the reason for #5 was that the conservative work ethic drives people to get back to work, while liberals feel no qualms about staying and chatting--even if their employer is expecting them to return immediately.
11.4.2008 11:15am
www51eo (www):
11.4.2008 11:21am
AndrewK (mail):
.... or I could read exit polls, realize this, and assume that it's close if Obama is polling less than 70%.
11.4.2008 11:28am
JB:
Actually, I think exit polls will be biased toward McCain. #6 will be a tremendous issue, given the difficulties polls have had with voter turnout models this year. Obama has won early voting pretty handily, but I think that's mostly his strongest partisans voting, so he should be weaker on election day than he is overall.

I'd say if Obama is winning today's exit polls at all, he's winning in a landslide.
11.4.2008 11:36am
Bored Lawyer:
What do you mean by "ignore?" I think some believe it means "vote anyway." In other words, even if the networks announce that Candidate X has won (or has won State Y), you should still vote regardless.

I never understood the logic behind not voting in this situation. An election is not a horse race. A vote is one's opportunity to be heard in a democracy -- regardless of whether you pick the winner or the loser. I am not going to change my vote or be dissuaded from voting just because someone announces that they project the other guy won.
11.4.2008 11:38am
David R:
The problem is that people tell the truth to the pollster but lie in the voting booth.
11.4.2008 11:48am
darelf:
Also, people after the fact care about the popular vote. So even if you cast a McCain vote in California knowing it isn't going to give him that state, you are adding to the popular vote tally. Whoever wins the EC will also be judged by his total popular vote tally as well.

Please vote!
11.4.2008 11:51am
Calculated Risk:
If you know that exit polls are systematically flawed in favor of one candidate, you can make mental adjustments accordingly. That isn't a reason to ignore them.

If all you mean by "ignore" is that people should vote regardless of exit polls, then I agree. But if you mean they shouldn't even pay attention to his information if they are curious about how the election is turning out, I disagree.
11.4.2008 12:02pm
Daniel Chapman (mail):
Nah... sit home and watch the election on TV. The rest of you decrease the expected value of my vote and increase the cost in time spent waiting in line.

Please don't vote!
11.4.2008 12:15pm
Gary McGath (www):
I declined to be exit-polled this morning, mostly because I don't like it when the media announce the winner at 10 AM based on exit polls. (As I declined and was rushing past the exit poller, I recognized him as a friend of mine -- but still declined.)
11.4.2008 12:50pm
New World Dan (www):
Exit polls really only tell the story for races where we already know the result. I've had the last month to accept President Obama. There are a lot of local races here in Minnesota where I really don't have a good prediction for how they'll break.

Most polls I happily participate in, though I've never been offered a spot in an exit poll. I don't see the utility in predicting winners, but rather in voting habits. I like participating in polls in general because most use a fairly small sample size. Plus, my answers are usually not on the pollster's list of choices. :)
11.4.2008 1:31pm
Michael Drake (mail) (www):
"I thought the reason for #5 was that the conservative work ethic drives people to get back to work, while liberals feel no qualms about staying and chatting...."

No, it's more our hatred of America generally.
11.4.2008 2:02pm
LM (mail):
David R:

The problem is that people tell the truth to the pollster but lie in the voting booth.

I think, kidding aside, that's actually about right.
11.4.2008 3:04pm
David Warner:
LM,

"I think, kidding aside, that's actually about right."

I think that the word think deserves an apology.
11.4.2008 4:11pm
GD (mail):
Exit polls and the extensive statistical models behind them have been composed by the best and the brightest based on all available historical data and the latest in computer technology. To these suggest that these systems might possibly be flawed is to call into question the entire system of MBS, CDOs, CDS, etc. that underpin our global financial system and have been designed in a similar fashion.
11.4.2008 4:26pm
LM (mail):
David Warner:

I think that the word think deserves an apology.

You don't think a lot of people express ideals they aspire to, but when safe from view sometimes act on baser motives?
11.4.2008 5:27pm