Persistence of close personal ties over a 12-year period

Using data on 60 intentional communities from the Urban Communes Data Set, we examine factors related to the persistence of ties 12 years later, when nearly all members had left the groups. We find strong evidence of triadic effects—people are more likely to remain in contact with others when they share patterns of contact with third parties. Such triadic effects retain importance even when we use alternative measures of contact, and when we control for individual-, dyadic-, and group-level effects including geographic separation. When we examine friendship as opposed to contact, we find that the triadic effects can be decomposed into some effects pertaining to hierarchy and other effects pertaining to reciprocation, giving us a sense of how networks structure themselves over time. © 2005 Elsevier B.V. All rights reserved.