Don’t Blame the Polls

Try as they might, pollsters can never account for one thing: human psychology.

A combination picture shows Democratic presidential nominee Joe Biden in Wilmington, Delaware, and U.S. President Donald Trump in Washington, D.C., early Nov. 4.
A combination picture shows Democratic presidential nominee Joe Biden in Wilmington, Delaware, and U.S. President Donald Trump in Washington, D.C., early Nov. 4.
A combination picture shows Democratic presidential nominee Joe Biden in Wilmington, Delaware, and U.S. President Donald Trump in Washington, D.C., early Nov. 4. Angela Weiss and Mandel Ngan/AFP/Getty Images

Just like after the 2016 U.S. presidential election, American pollsters are under attack. Back then, they failed to predict the victory of Donald Trump. This time around, instead, Joe Biden is on course to become president with a much smaller margin of victory than originally expected. Immediately before Election Day, he was leading nationwide polls by more than 7 percentage points over incumbent President Trump, a lead that was almost three times higher the one enjoyed by Democratic Party contender Hillary Clinton four years ago. And in the final rush of polling, Biden also managed to surpass Trump in Florida, Georgia, and Ohio—all states that, in the end, appeared to have voted for the Republican candidate.

But polls are two-sided games. At one end, there are the pollsters, who ask the questions and are responsible for designing their surveys in a methodologically sound way. At the other, there are the interviewees, who are expected to answer faithfully. Obviously, biased responses in polls skew the data, leading to inaccurate predictions. And it is not unusual for psychology to trump statistics.

Since 2016, pollsters have worked tirelessly to improve the quality of the underlying methodology of their surveys. In particular, they tried to address the sampling bias that four years ago led to underestimates for turnout among specific demographic groups (white voters in particular) who were decisive for Trump’s victory. Websites like FiveThirtyEight also aggregate polls from different sources by assigning a rating to each of them, based on accuracy scores that are adjusted for the poll’s sample size, the performance of other polls surveying the same race, statistical biases, and other factors.

Just like after the 2016 U.S. presidential election, American pollsters are under attack. Back then, they failed to predict the victory of Donald Trump. This time around, instead, Joe Biden is on course to become president with a much smaller margin of victory than originally expected. Immediately before Election Day, he was leading nationwide polls by more than 7 percentage points over incumbent President Trump, a lead that was almost three times higher the one enjoyed by Democratic Party contender Hillary Clinton four years ago. And in the final rush of polling, Biden also managed to surpass Trump in Florida, Georgia, and Ohio—all states that, in the end, appeared to have voted for the Republican candidate.

But polls are two-sided games. At one end, there are the pollsters, who ask the questions and are responsible for designing their surveys in a methodologically sound way. At the other, there are the interviewees, who are expected to answer faithfully. Obviously, biased responses in polls skew the data, leading to inaccurate predictions. And it is not unusual for psychology to trump statistics.

Since 2016, pollsters have worked tirelessly to improve the quality of the underlying methodology of their surveys. In particular, they tried to address the sampling bias that four years ago led to underestimates for turnout among specific demographic groups (white voters in particular) who were decisive for Trump’s victory. Websites like FiveThirtyEight also aggregate polls from different sources by assigning a rating to each of them, based on accuracy scores that are adjusted for the poll’s sample size, the performance of other polls surveying the same race, statistical biases, and other factors.

Of course, even the most statistically meticulous poll will always provide a partial view of reality. Each choice concerning its structure is subjective and discretionary. In the end, its accuracy will always lie within a statistical interval of confidence—that is, a specific margin of error, up or down.

And this interval might become especially wide if those interviewed lie or do not respond at all. While nobody can confidently say anything about those who might give fake responses, we know that this year undecided voters amounted to around 5 percent of Americans ahead of the vote. That’s a sufficient number of people to alter the outcome of the election. Some may have been genuinely unsure of whether to vote for Trump or Biden. But others, particularly moderate Republicans in affluent areas, might have simply not wanted to state their preference for a polarizing figure like Trump. In statistics, this is the so-called social desirability bias—the desire to appear to do what is perceived as the socially correct thing to do. For similar reasons, polls might have failed to fully capture the shift of Hispanic voters toward Trump in some key states.

And that is an important lesson: Even as technology and big data keep improving the quality of the polling on the pollsters’ side, at the other end the respondents will always be human beings, with their own psychologies, biases, and emotions. If we forget it, we will set ourselves up for new electoral surprises every time.

Edoardo Campanella is a Future World fellow at IE University’s Center for the Governance of Change in Madrid and the co-author, with Marta Dassù, of Anglo Nostalgia: The Politics of Emotion in a Fractured West.

More from Foreign Policy

Soldiers of the P18 Gotland Regiment of the Swedish Army camouflage an armoured vehicle during a field exercise near Visby on the Swedish island of Gotland on May 17.
Soldiers of the P18 Gotland Regiment of the Swedish Army camouflage an armoured vehicle during a field exercise near Visby on the Swedish island of Gotland on May 17.

What Are Sweden and Finland Thinking?

European leaders have reassessed Russia’s intentions and are balancing against the threat that Putin poses to the territorial status quo. 

Ukrainian infantry take part in a training exercise with tanks near Dnipropetrovsk oblast, Ukraine, less than 50 miles from the front lines, on May 9.
Ukrainian infantry take part in a training exercise with tanks near Dnipropetrovsk oblast, Ukraine, less than 50 miles from the front lines, on May 9.

The Window To Expel Russia From Ukraine Is Now

Russia is digging in across the southeast.

U.S. President Joe Biden and Secretary of State Antony Blinken participate in a virtual summit with the leaders of Quadrilateral Security Dialogue countries at the White House in Washington on March 12.
U.S. President Joe Biden and Secretary of State Antony Blinken participate in a virtual summit with the leaders of Quadrilateral Security Dialogue countries at the White House in Washington on March 12.

Why China Is Paranoid About the Quad

Beijing has long lived with U.S. alliances in Asia, but a realigned India would change the game.

Members of the National Defence Training Association of Finland attend a training.
Members of the National Defence Training Association of Finland attend a training.

Finns Show Up for Conscription. Russians Dodge It.

Two seemingly similar systems produce very different militaries.