Newman, M. E. J.
Recent work has demonstrated that many networks have broad distributions of vertex degree. Here we show that this has a substantial impact on the shape of ego-centered networks and on concepts and methods based on ego-centered networks, such as snowball sampling and the "ripple effect". In particular, we argue that one's acquaintances, one's immediate neighbors in the acquaintance network, are far from being a random sample of the population, and that this biases the numbers of neighbors two and more steps away. We demonstrate this concept using data on academic collaboration networks. (C) 2002 Elsevier Science B.V. All rights reserved.