The 2020 election polls were less accurate than those in 2016, our ranking finds.

Table of Contents1 After 2016, pollsters worked to fix problems 2 How we did our research3 What went wrong? So how did pollsters do in 2020? After 2016, pollsters worked to fix problems After the 2016 election, we worked with political scientist Aaron Weinschenk to release analyses, revealing 2016’s final, […]

So how did pollsters do in 2020?

After 2016, pollsters worked to fix problems

After the 2016 election, we worked with political scientist Aaron Weinschenk to release analyses, revealing 2016’s final, national pre-election polls were actually more accurate than they had been in 2012. They pretty closely forecast the popular vote, even if Donald Trump snagged victory in the electoral college. We found a slight pro-Democratic bias that was mostly not statistically significant.

That suggests that, overall, the 2016 national pre-election polls were generally accurate and unbiased. That year’s state-level polls similarly underestimated Republican support, but here too these biases were generally statistically insignificant. The larger problem — at least for those who wanted to know the outcome in advance — was too few quality statewide polls in key battleground states, compared with previous years.

Nevertheless, the discrepancy between poll projections and the eventual outcome pushed many pollsters to reconsider their methods. Survey researchers scrutinized the 2016 polls and considered an array of factors that potentially contributed to underestimating President Trump’s support. These included: failure to adjust weighting procedures to account for elevated survey participation among college graduates, who disproportionately went for Clinton; possible “shy” Trump voters; people who decided which candidate to support late in the campaign, and disproportionate increases in turnout among Republicans. As a result, many polling firms changed their weighting procedures.

How we did our research

The figure below shows our accuracy rankings. As you can see, two of the 14 polls were highly accurate. Both the Investor’s Business Daily/TIPP and The Hill/HarrisX polls had Joe Biden ahead by 4 percentage points — and Biden is currently 3.8 percentage points ahead of Trump in the national popular vote.

Almost all of the remaining polls — except the Rasmussen poll released Nov. 1 — overestimated support for Biden. Taken as a group, the average bias in the 2020 polls overall is -0.085, which is not statistically significant. However, these five polls’ pro-Democratic bias is statistically significant: Economist/YouGov, CNBC/Change Research, NBC News/Wall Street Journal, USC Dornslife, and Quinnipiac.

We also compared accuracy over time using available accuracy scores for election cycles since 1996. The figure below shows the mean accuracy score for the final, national pre-election polls in the 2020 presidential election in historical context. As you can see, this cycle’s polls were, as a group, among the least accurate since 1996.

What went wrong?

A handful of national polls navigated this complicated terrain with great success. Overall, however, 2020’s presidential pre-election polls were not quite triumphant.

Costas Panagopoulos is professor of political science and chair in the Department of Political Science at Northeastern University.

Kyle Endres is assistant professor of political science at the University of Northern Iowa.

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