Part 1. Development of a Methodology for Network Research on Social Cohesion
Longitudinal Network Studies and Predictive Social Cohesion Theory D.R. WHITE, University of California Irvine, NSF BCS-9978282
   An operational definition of social cohesion based on network connectivity measures cohesiveness as the minimum number k of actors whose absence would disconnect a group.  Two members of a group with cohesion level k automatically have at least k different ways of being connected through independent paths. 
  A test of the measure is exemplified by successful prediction of how a group, studied longitudinally during a period of conflict between leaders, divides into two (Fig 1), based on cohesion and distance.
Reference:
   2001 Douglas R. White and Frank Harary, The Cohesiveness of Blocks in Social Networks: Node Connectivity and Conditional Density, vol. 31, no. 1 in  Sociological Methodology 2001: 305-359. Blackwell Publishers, Inc., Boston, USA.
Fig 1. Snapshot of friendships at successive points in time in a longitudinal study of friendship in a Karate club, with leaders labeled T and A and levels of cohesion coded by color. When members with ties to both leaders T and A are forced to choose between them, removing the red lines, two cohesive hierarchies form that bifurcate the club.
Data source: Wayne Zachary, 1977. An Information Flow Model for Conflict and Fission in Small Groups. Journal of Anthropological Research 33:452-73.
Connectivity: Blue=4 Red=3 Green=2 Yellow=1
T
A