The SCI is relative.
If one SCI value is twice another, the friendship likelihood is twice as high. The exact units matter less than ratios and patterns.
Social Connectedness Index
The Social Connectedness Index (SCI) is a globally comparable measure of the relative probability that Facebook users in two locations are friends.
What the number means
The SCI answers a simple question: if you pick one person in one place and another person somewhere else, how likely are they to be friends?
The SCI is symmetric.
The connection from A to B is the same as the connection from B to A, because Facebook friendships are mutual links.
The SCI is privacy protected.
The public data are aggregated and differentially private. The tools never expose person-level friendship records.
Why it matters
By leveraging social network data, the SCI overcomes longstanding measurement challenges and enables new lines of research on the role of social networks in determining economic, social, and political outcomes.
Markets & trade
Social connectedness is an important determinant of international and subnational trade flows.
Health & mobility
The SCI has shown that the geographic spread of COVID-19 correlates with social network structure.
Migration flows
Friendship networks can reveal where people may have family, friends, or support systems when they move or are displaced.
Social clusters
Administrative borders are not always social borders. SCI clusters show which regions behave like connected communities.
Explore the tools
Explore connections live, make publication-ready maps, or group regions into connected communities.
Interactive Explorer
Click any country or region on an interactive globe and watch it light up with where it's most connected. The fastest way to explore the data to discover surprising links.
Start exploring →Map Maker
Build polished, publication-quality SCI maps with full control over geography, colors, breaks, and titles — then download as an image or video to share them.
Make a map →Connected Communities
Pick a region or country and a number of clusters, then watch its places group by how tightly they're connected — revealing which truly belong together.
Find clusters →If you use the Social Connectedness Index in your work, please cite:
- Johnston, D., Kuchler, T., Kulkarni, M., & Stroebel, J. (2026). The Social Connectedness Index: A Large-Scale Dataset of Social Ties Across Geographic Locations. Data in Brief, 67, 112905.
- Bailey, M., Cao, R., Kuchler, T., Stroebel, J., & Wong, A. (2018). Social Connectedness: Measurement, Determinants, and Effects. Journal of Economic Perspectives, 32(3), 259-280.
Data: Facebook Social Connectedness Index (Humanitarian Data Exchange)