Abstract Social information is particularly prominent in digital settings where the design of platforms can more easily give real-time information about the behaviour of peers and reference groups and thereby stimulate political activity. Changes to these platforms can generate natural experiments allowing an assessment of the impact of changes in social information and design on participation. This paper investigates the impact of the introduction of trending information on the homepage of the UK government petitions platform. Using interrupted time series and a regression discontinuity design, we find that the introduction of the trending feature had no statistically significant effect on the overall number of signatures per day, but that the distribution of signatures across petitions changes-the most popular petitions gain even more signatures at the expense of those with less signatories. We find significant differences between petitions trending at different ranks, even after controlling for each petition's individual growth prior to trending. The findings suggest a non-negligible group of individuals visit the homepage of the site looking for petitions to sign and therefore see the list of trending petitions, and a significant proportion of this group responds to the social information that it provides. These findings contribute to our understanding of how social information, and the form in which it is presented, affects individual political behaviour in digital settings. * Authors are in alphabetical order and made equal contributions. Social information-information about what others are doing or have done-has always been a powerful influence on political behaviour. But in digital settings people are exposed to more social information than ever before. When confronted with an item of news or information, or invited to participate in a political mobilization or campaign, users of social media know in real-time how many other people have 'liked', shared, downloaded, 'favourited', 'retweeted', reviewed or commented upon that item. They may be able to read other individuals' comments and feedback, and they may be recommended another item on the basis of the behaviour of other people. Indeed real-time social information is so ubiquitous that it is no longer easy to distinguish its effect on individual behaviour, given that it is the default setting for most activities online. However, the more that political participation takes place online-and therefore under conditions of greater social information-the more important it becomes to understand the influence of social information at the micro level. Platform changes can provide a valuable opportunity to isolate and understand social information effects on contemporary political behaviour, and thereby provide valuable insight into the dynamics of contemporary political mobilization. Platform changes can provide conditions for a natural experiment as visitors to the site just before and after the change experience the change as if it were random (Dunning, 2012) . Under these conditions, there is no reason to expect different behaviour before and after the change that cannot be directly attributed to the change. This paper analyses the effect of one such change-the introduction of trending information onto the homepage of the UK government petitions platform-and its impact on petition signing. It uses data pertaining to internet-based mobilizations around petitions, generated from the current electronic petitions platform in the UK, which was developed by the UK Cabinet Office for the incoming Coalition Government in 2010 and launched in August 2011. The data collected on the site since its launch provides an example of real-time transactional data on this popular form of political participation for a whole population (N = all), and thereby represents so-called 'big data'. First, we review some recent literature on social information and participation and relate it to online settings. Second, we provide some background on petitioning as a form of collective action and outline the distinctive features of the e-petition platform we examine here. Third, we present the petitions data and analyse it with interrupted time series analysis and a regression discontinuity design. We discuss the key findings from the data, which suggest that a small but significant group of users (who we label 'aimless petitioners') are indeed influenced by the trending information. Fourth, we use site analytics data from the petitions platform to understand further the size, constituency and behaviour of this group of users. To conclude, we discuss the implications of our findings for political science research into political participation in digital settings and for those who design portals aimed at citizen engagement.
A study of the UK government petitions platform showed that introducing trending information on the homepage increased the inequality in the number of signatures across petitions REF .
Investigating Political Participation and Social Information Using Big Data and a Natural Experiment
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Mathematics Computer Science Physics