Compare methods

	E-I Index	Blockmodeling	Isolation Index
Field	Sociology	Sociology	Sociology
Family	Process / pipeline	Process / pipeline	Process / pipeline
Year of origin	1988	1976	1954
Originator	David Krackhardt & Robert Stern	Harrison White, Scott Boorman & Ronald Breiger	Wendell Bell (formalization of P* indices)
Type	Index of the relative balance of between-group versus within-group ties	Network partitioning into positions and a reduced role structure	Exposure-dimension segregation index
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.	Bell, W. (1954). A probability model for the measurement of ecological segregation. Social Forces, 32(4), 357–364.
Aliases	EI index, external-internal index, Krackhardt-Stern E-I ratio, E/I ratio	block modeling, blockmodel analysis, generalized blockmodeling, CONCOR	P* isolation index, interaction index, exposure index, Bell isolation index
Related	5	4	5
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.	The isolation index measures the exposure dimension of segregation: the extent to which members of a minority group are exposed only to one another rather than to members of other groups. It answers the question 'what is the own-group share of the typical neighbor (or classmate, or coworker) that a member of the focal group encounters?' Unlike evenness measures, it depends on the relative size of the group as well as its spatial distribution.