In 1982, Californians voted for their next governor. Exit polls favoured Tom Bradley, the African American Mayor of Los Angeles[i]. However,George Deukmejian(his white opponent) ultimately won the race. Experts attributed the unexpected outcome to the “Bradley effect”[ii]– the idea that some voters lied to pollsters about their intentions to avoid the appearance of racism (a “social desirability bias”[iii]). Other voters may have simply refused to answer the question out of discomfort.
Less than a week ago, Donald Trump was sworn in as the 45th President of the United States. It was an unexpected outcome for those who followed polls in 2016. Even on the eve of the election, the New York Times poll predicted that Clinton had an 84% chance of winning. Pollster Nate Silver and the Princeton Election Consortium calculated a 71% chance and 95-99% chance, respectively. So why did “serious predictors completely misjudge Trump’s chances of victory”? Experts point to several likely factors, including: