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6 maltatoday, WEDNESDAY, 16 NOVEMBER 2016 News What went wrong with After Brexit and Trump's surprise victory the credibility of opinion polls has received a drubbing. Have the polls really got it so wrong and if so why, JAMES DEBONO asks How wrong were the polls? The US were faced with two three kind of polls; national polls showing how the candidates stood in the popular vote, polls in each state particularly in swing states which ultimately determine who fins and finally an assessment of different polls showing the prob- ability of a Hillary Clinton or Donald Trump win. Not far off the mark Since the US President is not elected by a majority of the popu- lar vote but by a majority in the electoral collage based on a win- ner takes all basis - in which a candidate wins all the votes allo- cated to each one of 50 states - na- tional polls assessing the popular vote are simply an indication on how candidates are performing. Polling site Real Clear Politics' last survey polling average (based on results of different polling in- stitutes) found Clinton holding a 3.2-point lead (46.8 to 43.6), down 3 points since mid-October. This was a clear indication that the election was close. While most polls showed Clinton leading by 3 to 6 points, the LA Times poll showed Trump leading by 3 points. Clinton is set to win the popular vote by around 1.5%, therefore on this level the polls were not far off the mark, rightly predicting Clin- ton winning the popular vote. The only fluke was a surge in support for Clinton in October as a reaction to recordings exposing Trump's misogynist character. But this surge had dissipated in the last week of the campaign after the FBI's controversial decision to resurrect an investigation in Clin- ton's use of her private email. In the final instance, US polls were more reliable than British polls predicting a Remain victory in the June Brexit referendum. But it is clear that polls assess- ing the national strength of candi- dates are not a credible indication on who would win. In fact the re- sult simply confirms the increas- ing discrepancy between the pop- ular vote and the actual outcome of elections, one that makes na- tional overall polls that simulate the popular vote less relevant to predictions over time. Mixed verdict on state polls Of more crucial importance were polls conducted on a state level. State polls showed Trump going into Election Day edging out Clinton in some key battle- ground states, including Nevada and North Carolina, leading by 3 or more points in Iowa, Arizona and Ohio. In the tightly contested swing state of Florida, Trump held a 0.2% advantage. He also closed the gap signifi- cantly in Pennsylvania, Colorado and Michigan, but remained down by 2, 3 and 3.4 points in the states, respectively. On Election Day, Trump man- aged to win Ohio, Pennsylvania, Michigan, North Carolina and Florida. Polls in the final weeks of the campaign definitely showed Trump making significant gains in swing states, but with the gap being so small in states like Flori- da, it was hard to imagine Trump to make such a clean sweep. For while Clinton had sev- eral paths to the White House, Trump's strategy relied on him winning all the Rust Belt states including Pennsylvania, Ohio and unlikely ones like Michigan and North Carolina. This is what Trump did exactly on election night while also winning Florida. Flawed predictions This leads us to the most dan- gerous of all predictions made by pollsters; that on who was the most likely to win a majority in the Electoral College. FiveThirtyEight's forecast gave Trump much better odds than other polling-based models. Their final forecast, issued early Tues- day evening, had Trump with a 29% chance of winning the Elec - toral College. By comparison, other models tracked by The New York Times put Trump's odds at: 15%, 8%, 2% and less than 1%. As it turned out, Trump won largely for the same reasons that FiveThirtyEight chief pollster Nate Silver's model had given him better odds than others i.e. the high number of undecided voters had ended up breaking in Trump's favour, and Clinton had under- performed in the Midwest. Reasons why polls went wrong 1. Polling in smart phone era The advent of mobile and smart phones has made finding accurate and random samples of voters to poll more difficult. Prior to mo- bile phones, the universality of landline telephones made finding random and representative sam- ples easy, as pollsters could just pick random names out of phone books, call potential voters, and talk them through interviews. This method ensured high re- sponse rates among which rough- ly reflected the class and occu- pational structure of society. In contrast mobile phone numbers are not usually publicly listed, making it harder and harder to find representative samples. Moreover demographic differ- ences exist between people still relying on landlines and those who can only be reached on cell phones. Coupled to this are changing working and lifestyle patterns of people who are rarely at home, or only at home at times when they are least likely to be reached by pollsters. Various online survey methods have been used to supplement more expensive phone methods, but they often also suffer from bias and are generally considered of lower quality than other polls. 2. Trump changed the electorate The main reality check for poll- sters is the past voting patterns of respondents who are asked whom they have voted for in previous elections. Respondents are also asked about past voting inten- tions and this gives pollsters the opportunity to assess shifts from one party or candidate to another. Moreover this also shows how re- liable one sample is. Unlike Malta where more than 90% of the pop- ulation votes, the US is a country were only half the electorate votes. Therefore any change in the com- position of the electorate like for example an increase in turnout Hillary Clinton went into Election Day with a 3.2 point lead but the actual result handed the keys to the White House to her rival Donald Trump