A computer implemented method for constructing and analyzing a graph representing a social network of a plurality of members, wherein the method comprises: obtaining from a plurality of computer-networked devices, each associated with a distinct member, data indicative of transfer of information (I) between the members by analyzing the communication between their respective devices; detecting, based on the communication analysis, at least one relationship between the plurality of members; determining active or passive coefficients for active or passive transfer of information for at least implicit communication between each plurality of members having said relationship; analyzing said implicit communication according to transfer of information, to determine a level of influence for each member; and determining at least one key member of the social network based on said level of influence.
Analyzing transactional data