Donald Trump's campaign is said to have spent 44 million dollars on Facebook, running 175,000 variations of political adverts during the election campaign, compared to a spend of 28 million dollars by Hillary Clinton's campaign. Was this money well-spent?

New research from the University of Warwick, ETH Zurich and the University Carlos III in Madrid has demonstrated the effectiveness of micro-targeted political advertising on social media.

Online political campaigns targeting Facebook users by gender, location and political allegiance significantly increased support for Republican candidate Donald Trump. The micro-targeted campaigns exploiting Facebook's profiling tools were highly effective both in persuading undecided voters to support Mr Trump, and in persuading Republican supporters to turn out on polling day.

The effects of intensive online campaigning were strongest among voters who used Facebook regularly; among those who relied upon it as their main source of news; and among voters without university or college-level education.

The paper, Politics in the Facebook Era: Evidence from the 2016 US Presidential Elections, is believed to be the first analysis of the extent of political campaigns conducted on Facebook to micro-target voters, and of the effect that those campaigns had on voting behaviour.

Dr Michela Redoano, Associate Professor in the University of Warwick Department of Economics said: "Digital campaigning is much cheaper than campaigns in traditional media also thanks to the exploitation of social networks, it is easily accessible, and it is virtually free of regulation.

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"Thanks to predictive analytics, companies like Facebook offer a toolkit for targeting voters at an extremely granular level based on their previous online behaviour. These online campaign channels are potentially very powerful political instruments.

"It is therefore vital that we understand how political campaigns on social media work, their impact on voter behaviour, and, ultimately, on election results."

Dr Federica Liberini from ETH Zurich, said: "Our research allowed us to build a simple measure for tracking the intensity of political campaigns conducted on social media. In the context of the 2016 US Presidential elections, we find that political micro-targeting was particularly effective when based on ideology and gender or educational level, and much less so when based on race or age. Our results show that social media effectively empowered politicians to influence key groups of voters in electoral races, and it is further evidence that recent political outcomes, such as Brexit and the election of President Trump, might be largely due to the use of data analytics."

Dr Antonio Russo also from ETH Zurich added: "Our finding that Facebook had a strong effect on turnout suggests that social media has great potential for stimulating the political participation of people who would otherwise have lost interest in politics. In a world where confidence in democracy is dwindling, I believe this is good news. However, we still have much to learn about whether the information that voters are exposed to on social media really helps them make informed choices"

Dr Angel Cuevas and Dr Ruben Cuevas from the University Carlos III in Madrid commented: "This paper contributes to an incipient body of literature that is using Facebook data, in a completely privacy-preserving manner, as a novel and highly valuable data source to address important socio-economic questions.

"In this line, we have already used Facebook data to measure the gender divide worldwide and we are using in a still on-going work to create a new methodology to measure culture. We would also like to highlight that this data is serving to promote fruitful multidisciplinary collaboration between computer scientists and social scientists."

The researchers also show that reading about politics on Facebook does not improve political knowledge in the way that reading a newspaper does.

"This is a worrying scenario, since more and more people substitute social media as a major source of information," Dr Redoano added.

The paper, Politics in the Facebook Era: Evidence from the 2016 US Presidential Elections by Federica Liberini, Michela Redoano, Antonio Russo, Angel Cuevas, and Ruben Cuevas, is published in the University of Warwick Centre for Competitive Advantage in the Global Economy (CAGE) working paper series, available online at: https://warwick.ac.uk/fac/soc/economics/research/centres/cage/publications/workingpapers