The Problem With a Crowd of New Online Polls

The polls were one of the big winners of the 2012 presidential election.They showed Barack Obama ahead, even though many believed a weak economy would propel Mitt Romney to victory.The polls conducted online were among the biggest winners of all.The most prominent online pollsters — Google Consumer Surveys, Reuters/Ipsos and YouGov — all produced good or excellent results.

With the right statistical adjustments, even a poll of Xbox users fared well.These successes seemed to herald the dawn of a new era of public opinion research, one in which pollsters could produce accurate surveys cheaply, by marrying online polls with big data and advanced statistical techniques.A decade later, the new era has arrived — and has fallen far short of its promise.Ever since their 2012 breakout performance, the public polls relying exclusively on data from so-called online opt-in panels have underperformed the competition.Only YouGov, long at the cutting edge of this kind of polling, is still producing reasonably accurate results with these panels.Many of the online pollsters who excelled in 2012 have left public polling altogether:Google Consumer Surveys — by 538’s reckoning perhaps the best poll of 2012 — was arguably the single worst pollster in the 2016 election, and it has stepped out of the political polling game.The Xbox poll did not return.

The researchers behind it used a different online survey platform, Pollfish, to predict Hillary Clinton victories in Texas and Ohio in 2016.And last year, Reuters/Ipsos abandoned opt-in, or nonprobability, polling.There are still Reuters/Ipsos polls, but they’re now traditional surveys with panelists recruited by mail.Nonetheless, a majority of polls are now conducted in exactly this way: fielded online using people who joined (that is, opted into) a panel to take a survey, whether by clicking on a banner ad or via an app.

Traditional polling, in contrast, attempts to take a random sample of the population, whether by calli...