“It is … a mistake to observe errors in an election such as 2016 that featured late movement and a somewhat unusual turnout pattern, and conclude that all polls are broken.” the authors wrote. “Well-designed and rigorously executed surveys are still able to produce valuable, accurate information about the attitudes and experiences of the U.S. public.”

Their research found no evidence of a consistent bias toward one party in recent polling, they noted, nor that a cohort of “shy” Trump voters were deliberately hiding their choices from pollsters.

Instead, there was a perfect storm of more prosaic issues ― some potentially fixable, others less so, and some seemingly innate to the practice of polling itself. In the fixable camp: College graduates, who were more likely to support Hillary Clinton, were overrepresented in many polls.

Voters with higher levels of education have always been more likely to answer surveys, but in past elections, where education was less of a partisan fault line, this proved less of an issue. Since then, a number of university pollsters who didn’t already include education on the list of variables used to weight their results have begun doing so, although others have found the change to be less useful to their situations.