1. A method comprising: by one or more computing devices, for one or more elements of information relating to a subject matter, wherein the elements of information have been shared among a plurality of users of a social-networking system: calculating one or more first-order derivatives of a non-zero rate of sharing of the element of information; identifying, based at least in part on one or more of the first-order derivatives, one or more increases in the non-zero rate of sharing of the element of information among the users, wherein each of the increases comprises a first number of shares of the element of information over a first period of time being less than a second number of shares of the element of information over a second period of time following the first period of time; and identifying, from the plurality of the users of the social-networking system, one or more first users who caused one or more of the increases in the non-zero rate of sharing, wherein each of the first users shared the element of information at one or more times respectively associated with one or more of the increases in the non-zero rate of sharing; and by one or more computing devices, identifying one or more influencers associated with the subject matter from the first users identified for one or more of the elements of information.