Research paper by Lars Groeger and Francis Buttle, in European Journal of Marketing. This paper highlights some problems in the way word of mouth marketing campaign results are measured. Most WOMM agencies equate campaign reach to the total number of conversations. Therefore, if I tell 10 of my friends about the campaign product and each of those tells an average of 5 friends, then the campaign has reached 50 people. We establish that this simple mathematical formula is most likely very wrong because of the influence of social network transitivity. A fully transitive network is one in which every person is connected to every other person. Transitivity means that at least some of my friends are also likely to be friends with each other, as well as with me, and therefore the campaign message may reach some of my network more than once, reducing the campaign’s reach accordingly. Transitivity means you cannot assume that every conversation about the campaign is with a unique person.