We study coalition formation in “real time”, a situation in which coalition formation is intertwined with the ongoing receipt of pay-offs. Agreements are assumed to be permanently binding: They can only be altered with the full consent of existing signatories. For characteristic function games we prove that equilibrium processes—whether or not these are history dependent—must converge to efficient absorbing states. For three-player games with externalities each player has enough veto power that a general efficiency result can be established. However, there exist four-player games in which all Markov equilibria are inefficient from every initial condition, despite the ability to write permanently binding agreements.

Putnam defines social capital as “features of social organization, such as networks, norms and social trust that facilitate coordination and cooperation ” (Putnam 1995: 67). Social networks are typically associated with social trust and with norms that promote coordination and cooperation for mutual benefit. Strong ties between individuals, infused with norms of reciprocity and trust, are often thought to help cooperation among them. They would enable these groups and society as a whole to deal smoothly and effectively with multiple social and economic issue. Other authors have noted that, in different contexts, strongly bonded groups may have adverse consequences for others (such as Portes and Landolt (1996)) or for themselves (see for instance Akerlof (1976) or Basu (1986)). Based on our earlier work on risk sharing in groups and networks (Genicot and