Compare methods

	E-I Index	Blockmodeling
Field	Sociology	Sociology
Family	Process / pipeline	Process / pipeline
Year of origin	1988	1976
Originator	David Krackhardt & Robert Stern	Harrison White, Scott Boorman & Ronald Breiger
Type	Index of the relative balance of between-group versus within-group ties	Network partitioning into positions and a reduced role structure
Seminal source	Krackhardt, D., & Stern, R. N. (1988). Informal networks and organizational crises: An experimental simulation. Social Psychology Quarterly, 51(2), 123–140.	White, H. C., Boorman, S. A., & Breiger, R. L. (1976). Social structure from multiple networks. I. Blockmodels of roles and positions. American Journal of Sociology, 81(4), 730–780.
Aliases	EI index, external-internal index, Krackhardt-Stern E-I ratio, E/I ratio	block modeling, blockmodel analysis, generalized blockmodeling, CONCOR
Related	5	4
Summary	The external-internal (E-I) index, introduced by Krackhardt and Stern, measures the extent to which the ties of a group point outward to other groups versus inward to its own members. It is the number of between-group (external) ties minus the number of within-group (internal) ties, divided by the total number of ties. Ranging from −1 (all ties internal, perfect insularity) to +1 (all ties external), it is a compact summary of homophily and group closure that can be computed for a whole network, for each group, or for each node.	Blockmodeling is a family of methods that simplify a social network by partitioning its actors into positions — groups of actors who are equivalent in their pattern of ties — and summarizing the relations between positions as a compact image, or reduced role structure. Introduced by Harrison White, Scott Boorman, and Ronald Breiger in 1976, it shifts attention from individuals to the structural roles they occupy.