In 1936, the general-interest magazine Literary Digest asked ten million people which candidate they preferred for president: the Democratic incumbent Franklin D. Roosevelt, or the Republican challenger Alf Landon. Two million people responded, and they overwhelmingly picked Landon. When FDR won a second term, Literary Digest — which up to then had been known for the accuracy of its polling of presidential elections — was shamed out of existence; it wound up being subsumed by Time magazine in 1938.
How did Literary Digest get it so wrong? It used three readily-available lists of people for its polling: Telephone users, automobile owners, and its own subscribers. In 1936, persons in those three groups were much wealthier than the average American, and so Literary Digest‘s sample, while quite large, skewed heavily Republican.
In the years following World War Two, landline telephone use got cheaper and people got more prosperous, which meant that phone use became near-universal — a fact that pollsters have taken advantage of for decades. However, the growth in the number of cellphone-only telephone users is complicating things:
Say you want to reach a representative sample of the U.S. electorate for a presidential poll. The Obama-McCain race is relatively close these days, with the Democrat’s lead hovering around 5 to 6 points in most surveys. Someone tells you that he’s selected a sample that’s predominantly under 40 years of age (oops, that one favors Obama); disproportionately renters rather than homeowners (Obama-leaning again); full of college students (sounds like a Starbucks Obama thing to me) — and, for good measure, includes a higher proportion of blacks and Hispanics than the national population does.
At this point you throw up your hands and exclaim: “Why are we concentrating on such a pro-Obama universe? He could be leading by 20 points or more among those people!”
He could. He probably is. But in actuality, the sample I’ve described is either not being included at all in many national polls or is being undercounted. Why? Because I’m talking about the growing number of American cellphone users who have no other type of phone or who choose to go wireless for the vast majority of their interactive needs. And this election cycle — for the first, and perhaps only, time — this group has the chance to render presidential polls “wrong from the start”: potentially disguising at least 2 to 3 percentage points of Obama support and maybe more.
Why is this a big deal? This is why:
The most recent estimate places the number of “wireless” adult Americans at around 30 percent — with slightly more than half of those only using cellphones and the rest possessing both land lines and cellphones but using the latter far more often. Looking at the data over time, it is clear those numbers are getting higher each month. The 2004 presidential election exit poll conducted by the National Election Pool found that 7.1 percent of all voters in that election were cellphone-only. Recent data indicates that the percentage could be twice as high in 2008.
The problem is that pollsters hate polling cellphone-only users because they’re not legally allowed to machine-dial them — they have to be dialed manually, which means spending both more time and money to reach a group of people who are generally less cooperative with pollsters than are land-line users. But if the pollsters ignore them, polls will be getting ever-more inaccurate. (H/T Meteor Blades.)
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