We present an analysis of a person-to-person
recommendation network, consisting of 4 million people
who made 16 million recommendations on half a million
products. We observe the propagation of recommendations
and the cascade sizes, which we explain by a simple
stochastic model. We then establish how the
recommendation network grows over time and how effective
it is from the viewpoint of the sender and receiver of
the recommendations. While on average recommendations
are not very effective at inducing purchases and do not
spread very far, we present a model that successfully
identifies product and pricing categories for which
viral marketing seems to be very effective. pdf 2006
