Social media heavily changed the way we get informed and shape our opinions. Users’ polarization seems to dominate news consumption on Facebook. Through a massive analysis on 920 news outlets and 376 million users, we explore the anatomy of news consumption on Facebook on a global scale. We show that users tend to confine their attention on a limited set of pages, thus determining a sharp community structure among news outlets. Furthermore, our findings suggest that users have a more cosmopolitan perspective of the information space than news providers. We conclude with a simple model of selective exposure that well reproduces the observed connectivity patterns.

The advent of social media and microblogging platforms has radically changed the way we consume information and form opinions. In this paper, we explore the anatomy of the information space on Facebook by characterizing on a global scale the news consumption patterns of 376 million users over a time span of 6 y (January 2010 to December 2015). We find that users tend to focus on a limited set of pages, producing a sharp community structure among news outlets. We also find that the preferences of users and news providers differ. By tracking how Facebook pages “like” each other and examining their geolocation, we find that news providers are more geographically confined than users. We devise a simple model of selective exposure that reproduces the observed connectivity patterns.

Alarge body of research has addressed news consumption on online social media and its polarizing effect on public opinion (1⇓⇓⇓–5). Social media and microblogging platforms have changed the way we access information and form opinions. Communication has become increasingly personalized, both in the way messages are framed and how they are shared across social networks. Furthermore, according to a recent study (6), ∼63% of users acquire their news from social media, and these news are subject to the same popularity dynamics as other forms of content. Recent works (7) provide empirical evidence of the pivotal role of confirmation bias and selective exposure in online social dynamics. Users, indeed, tend to focus on specific narratives and join polarized groups (i.e., echo chambers) (8⇓–10), where they end up reinforcing their worldview [even if pieces of content are deliberately false (11, 12)] and dismissing contradictory information (13). Discussion and elaboration of narratives in such a segregated environment elicits group polarization and negatively influences user emotion (14⇓⇓–17). Therefore, in this paper, to better understand how echo chambers emerge, we explore the anatomy of news consumption on Facebook. We focus on how Facebook posts from news outlets are consumed and how user activity causes connectivity patterns to emerge. We analyze the interaction of 376 million users with all of the anglophone news outlets on Facebook listed in the European Media Monitor (18) over a 6-y time span, from January 2010 to December 2015. Using quantitative analysis, we find evidence that selective exposure plays a pivotal role in shaping news consumption online. Users tend to focus on a very limited set of pages and thus create a distinct community structure within these news outlets. We also find that the perspectives of the news outlets and the users differ. Our findings suggest that users have a more cosmopolitan perspective of the information space than news providers. Examining how pages “like” each other and taking into account their geolocation, we find geographically confined connectivity patterns. We conclude by devising a simple model of selective exposure that reproduces the observed connectivity patterns. We first analyze user behavior with respect to the information sources. We then analyze how user activity spans across these sources. Finally, we introduce a simple model that reproduces the observed dynamics. Our findings suggest that probably the main driver of misinformation diffusion is the polarization of users on specific narratives rather than the lack of fact-checked certifications.

Results and Discussion

Users’ Attention. News items on Facebook appear in posts that can be liked, commented, or shared by users. A like is usually a positive feedback on a news item. A share indicates a desire to spread a news item to friends. A comment can have multiple features and meanings and can generate collective debate. The likes, shares, and comments on Facebook posts present a heavy-tailed distribution (SI Appendix, 2. Attention Pattern). The lifetime of a post is the time period between the first and the last comment, and it presents a peak at 24 h. User activity is heterogeneous and the number of likes and comments ranges from very few (the majority) to hyperactivity. The Complementary Cumulative Distribution Function of the number of likes and comments for single users exhibits heavy tails (SI Appendix). The overall number of likes of each user is a good proxy for their engagement with Facebook news pages and the lifetime of each user can be approximated by the length of time between the date of their first comment and their last comment. These measures could provide important insights about news consumption. Our goal is to quantify the turnover of Facebook news sources by measuring the heterogeneity of user activity, and thus we measure the total number of pages a user interacts with. Fig. 1 shows the number of news sources a user interacts with for the lifetime (i.e., the distance in time between the first and last interaction with a post) and for increasing levels of engagement (i.e., the total number of likes). For a comparative analysis, we standardized between 0 and 1 both lifetime and engagement over the entire user set. Fig. 1 shows the results for the yearly time window (first column) and for the weekly (second column) and monthly (third column) rates. Note that a user usually interacts with a small number of news outlets and that higher levels of activity and longer lifetime correspond to a smaller number of sources. There is a natural tendency of the users to confine their activity on a limited set of pages. According to our findings, news consumption on Facebook is dominated by selective exposure. Fig. 1. Users’ attention patterns. (Top) Maximum number of unique news sources that users with increasing levels of standardized lifetime interacted with monthly, weekly, and yearly. (Bottom) Maximum number of unique news outlets which users with increasing levels of standardized activity interacted with monthly, weekly, and yearly.

Clusters and Users’ Polarization. User tendency to interact with few news sources might elicit page clusters. To test this hypothesis, we first characterize the emergent community structure of pages according to the users’ activity. We project the user page likes to derive the weighted graph G l p (and G c p ) in which nodes are pages and two pages are connected if a user likes (or comments on) both of them. The weight of a link on a projected graph is determined by the number of users the two pages have in common. Fig. 2 shows the backbone of G l p and G c p . Colors indicate node membership, as detected by the Fast Greedy (FG) algorithm (see Methods for further details). A histogram of community sizes is provided in SI Appendix, Fig. S5. To validate the community partitioning, we compare the membership of other community detection algorithms using the Rand method (19, 20) and find a high level of similarity (see SI Appendix for further details). We also compared the communities of G l p and G c p against each other using different community detection algorithms and find some level of similarity (see SI Appendix, Tables S3 and S4 in for further details). By examining the activity of users across the various clusters and measuring how they span across news outlets, we find that most users remain confined within specific clusters. To understand the relationship between page groupings and user behavior, we quantify the fraction of activity of user u in the largest communities w k u , k ∈ { 1...5 } , and the fraction of activity of user u in any other community w 0 u = 1 − ∑ k > 5 w k u . Fig. 3 shows the activity of users across the five largest communities (Fig. 3, Left) and compares this with a null model (Fig. 3, Right) in which user activity is randomly distributed. We find that users are strongly polarized and that their attention is confined to a single community of pages. User interaction to Facebook news outlets indicate a dominant community structure with sharply identified groups. Because users tend to focus on a small number of pages, the news sphere of Facebook is clustered and dominated by a precise community structure and users tend to focus their attention on a single group of news outlets. Fig. 2. Community structure. (Left) Backbone of the projections on pages of the users’ likes ( G l p ). (Right) Comments ( G c p ). The color of the nodes indicate the Fast Greedy community. Nodes in G l p are ordered according to the detected communities, whereas in G c p , the nodes follow the same order as in G l p . Fig. 3. Users Polarization. (Left) Activity of users across the five largest communities. (Right) Null model where users’ activity is randomly distributed. Vertices of the pentagon represent the five largest communities and the central point all of the remaining ones. The position of each dot is determined by the number of communities the users interacts with. The size and transparency indicate the number of users in that position.

Users’ and News Outlets’ Perspectives. Facebook pages can like each other. We use this pattern of favorite pages to create a graph of page preferences. In news outlets, these preferences can be used to compare the perspectives of users and news providers. We use the bipartite projection of the pages that users like G l p and define N p as the network of new outlets that like each other (i.e., N p is the network in which nodes are pages and links are pages liking each other). We analyze both networks by determining the geographical location of each page. Thus, each node is identified by its region and country, information provided by the European Media Monitor. To determine the community structure of both N p and G l p , we compare the outputs of different community detection algorithms (see Methods for further details). Fig. 4 shows the communities N p and G l p represented by taking into account the geographical location of the pages. In the graph, the external bundle groups pages by region, the middle bundle by nation, and node colors indicate community membership as identified by the FG algorithm. Note that in the plot, we use the backbone structure of the networks for visualization purposes (see Methods for further details). As in the previous section, we validate the partition found by the FG algorithm by comparing it with results from other community detection algorithms (see SI Appendix for further details). Using refs. 19 and 20, we compare the FG community structure of N p and G l p and do not find significant differences. When comparing the FG communities of N p and G l p (the projection of user likes) the similarity index is 0.67 , for N p and G c p (the projection of user comments), the similarity index is 0.69 (for the comparison with other community detection algorithms, see SI Appendix). Fig. 4 shows that in N p , the community structure is more confined within geographical boundaries than in G l p . Because the geographical location of pages also defines a community partitioning, we compare pages in G l p , G c p , and N p according to their community partitioning as detected by the FG algorithm and to their grouping according to the geographical location. The Rand similarity index among the partitions obtained by community detection algorithms and the partitions based on the geographical location is 0.71 for G l p , 0.72 for G c p , and 0.84 for N p (for the comparison with other community detection algorithms, see SI Appendix). This finding suggests that page communities are more locally confined than user interaction communities, which can span across nations and continents. Fig. 4. Pages and users’ communities and locations. Backbone of the projections on pages of the user likes reduced to the pages that appear in N p (Left) and the network of pages liking each other (Right). Inner nodes represent the pages and their color indicates the Fast Greedy community, middle track marks the country, and outer track the region as established by the European Media Monitor. Order of the inner nodes in both plots is done by region, country, and community, in that order. AF, Africa; AS, Asia; CA, Central America; EU, European Union; EU-C, EU Candidate; EU-O, EU Other; GL, Global; ME, Middle East; NA, North America; OC, Oceania; SA, South America.