Anthony Masters

Did Vote Leave’s overspending win the referendum for Brexit?

An Oxford professor’s claim that it was “very likely” that  overspending by Vote Leave swung the referendum for Brexit has taken off like wildfire. Professor Philip Howard’s analysis made the front page of yesterday’s Independent under the headline: ‘Illegal Facebook spending ‘won 2016 vote for Leave”. So do the numbers behind the headline add up? Prof Howard, director of the Oxford Internet Institute, calculated that:
  • Around 80 million Facebook users saw the Vote Leave campaign ads on social media during the period of excess spending;
  • 10 per cent of users clicked through;
  • 10 per cent of those users switched their vote as a result, giving over 800,000 switched voters.
This argument falls at each hurdle. An obvious point is that the 80 million Facebook users exceeds the entire UK population. This error appears to have been caused because Prof Howard added together daily users reached by Vote Leave. The posts are likely to have been seen by the same people across different days, meaning the total reach would be much smaller than 80 million. The numbers also wrongly conflate Vote Leave’s boosted paid reach, with people organically sharing its messages on Facebook. Organic sharing cost Vote Leave nothing, meaning that it could not have been part of their overspend. It is also worth asking another question: how many voters can Facebook reach? Recent research by the British Election Study team suggested that 55 per cent of Brits are on Facebook; Twitter is substantially less popular, with only 19 per cent of Brits using the site. If you assume that 55 per cent of the 46 million people registered to vote in Britain were on Facebook at the time of the referendum, at most an audience of 25.6 million electors could have been exposed to the adverts. The second claim, that 10 per cent of users clicked through on the advert, also seems dubious.

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