With just 42 days until the 2012 election, Americans are paying closer attention to presidential polling results. Not much has changed since the Republican and Democratic conventions: if you look at a rolling average of the last several months, President Obama has maintained a 3-4 point lead over Gov. Romney (within the statistical margin of error).
Traditionally, polling firms call landlines to get respondents’ voting preferences, but 33% of US households are now mobile-only. Research indicates that mobile-only households are considered to be more likely to vote Democratic, so more pollsters are making sure to include specific percentages of mobile users in each survey.
Before putting together a survey, pollsters must think in multiple dimensions so they can reach a representative sample of the electorate. Each poll includes select percentages of different population groups, such as:
- likely voters vs. registered voters
- Republicans vs. Democrats
- survey response rate
- live interviews vs. robocalls
“Landline vs. mobile phone” is a critical consideration, but because federal law prohibits robocalls to mobile numbers, pollsters must call these numbers to conduct live interviews. Historically, pollsters have faced similar challenges; in the 1936 election between President Franklin Roosevelt and Gov. Alf Landon of Kansas, the largest polling operation was Literary Digest, a weekly newsmagazine. In its election poll, Literary Digest mailed out 10 million postcards to people who were:
- members of specific clubs and organizations
- previously registered to vote
- listed in telephone directories
- registered car owners
After counting the surveys that were returned, Literary Digest reported that Landon would beat Roosevelt 66% to 33%. As it turned out, the 1936 election was one of the most lopsided ever — Roosevelt won 98% of the Electoral College and 60.8% of the popular vote! Did the magazine get it so wrong simply because they oversampled people with telephones (40% of the population)?
Not at all. Literary Digest sent out 10 million surveys, but only 2.3 million were returned, a dramatic nonresponse bias that wasn’t recognized until after Election Day. Additionally, the survey’s sample revealed a selection bias (magazine subscribers, car owners and telephone customers) that helped skew the results toward a more affluent crowd more likely to vote Republican.
Literary Digest folded not long after releasing its 1936 survey; more scientific polling outfits like Gallup, Roper and others soon became leaders in measuring public opinion. As we become more connected and data becomes easier to gather and crunch, it’s a safe bet that polling methodology will grow even more complex; for all we know, SMS could become the next major tool for measuring public opinion!
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