Second , we show that network composition , individual network central ity , and network structure are associated with important health behaviors and health and development outcomes in different context s across multiple levels of analysis and across distinct network types .
Lastly , we highlight the opportunities for health research ers and practitioners in LMICs to 1 ) design effective studies and interventions in LMICs that account for the sociocentric network positions of certain individuals and overall network structure , 2 ) measure the spread of outcomes or intervention externalities , and 3 ) enhance the effectiveness and efficiency of aid based on knowledge of social structure .
In low- and middle-income countries ( LMICs ) , naturally occurring social networks may be particularly vital to health outcomes as extended webs of social ties often are the principal source of various re sources .
A 61-million-person experiment in social influence and political mobilization
Human behaviour is thought to spread through face-to-face social networks , but it is difficult to identify social influence effects in observational studies , and it is unknown whether online social networks operate in the same way–. Here we report results from a r and omized controlled trial of  political mobilization messages delivered to 61 million Facebook users during the 2010 US congressional elections . The results show that the messages directly influenced political self-expression , information seeking and real-world voting behaviour of millions of people . Furthermore , the messages not only influenced the users who received them but also the users ’ friends , and friends of friends . The effect of social transmission on real-world voting was greater than the direct effect of the messages themselves , and nearly all the transmission occurred between ‘ close friends ’ who were more likely to have a face-to-face relationship . These results suggest that strong ties are instrumental for spreading both online and real-world behaviour in human social networks
Second , we show that network composition , individual network central ity , and network structure are associated with important health behaviors and health and development outcomes in different context s across multiple levels of analysis and across distinct network types .
Lastly , we highlight the opportunities for health research ers and practitioners in LMICs to 1 ) design effective studies and interventions in LMICs that account for the sociocentric network positions of certain individuals and overall network structure , 2 ) measure the spread of outcomes or intervention externalities , and 3 ) enhance the effectiveness and efficiency of aid based on knowledge of social structure .
In low- and middle-income countries ( LMICs ) , naturally occurring social networks may be particularly vital to health outcomes as extended webs of social ties often are the principal source of various re sources .