Compare methods

	Garfield's Law of Concentration	Scientific Collaboration Index (Co-Authorship Intensity)
Field	Bibliometrics	Bibliometrics
Family	Process / pipeline	Process / pipeline
Year of origin	1972	1983
Originator	Eugene Garfield	K. Subramanyam (review and Collaboration Index); S. M. Lawani (collaborative measures)
Type	Descriptive bibliometric law and core-journal identification pipeline	Descriptive bibliometric indicators of co-authorship intensity
Seminal source	Garfield, E. (1972). Citation analysis as a tool in journal evaluation. Science, 178(4060), 471-479.	Subramanyam, K. (1983). Bibliometric studies of research collaboration: A review. Journal of Information Science, 6(1), 33-38.
Aliases	Law of Concentration, Core Journal Concentration, Garfield Concentration Law	Degree of Collaboration, Collaborative Coefficient, Co-Authorship Intensity, Collaboration Index
Related	3	3
Summary	Garfield's Law of Concentration is the bibliometric principle that the bulk of the significant scientific literature is concentrated in a relatively small, largely multidisciplinary core of journals. Formulated by Eugene Garfield — founder of the Science Citation Index — and presented in his 1972 Science paper 'Citation analysis as a tool in journal evaluation', the law observes that when journals are ranked by how often they are cited, a core of perhaps 500 to 1,000 journals accounts for the overwhelming majority of all citations across all fields. Garfield framed it as a generalization and corollary of Bradford's earlier law of scattering: the long tail of any one discipline's literature is in large part composed of the cores of other disciplines, so a single multidisciplinary core covers science as a whole. The law underpins the rationale for selective, citation-based journal indexing.	The Scientific Collaboration Index family quantifies how collaborative a body of research is by analyzing the number of authors per paper. In his influential 1983 review of bibliometric studies of research collaboration, K. Subramanyam consolidated the main measures: the Degree of Collaboration (the proportion of multi-authored papers), the Collaboration Index (the mean number of authors per paper), and related indicators. S. M. Lawani and later Ajiferuke and colleagues refined these into the Collaborative Coefficient, which weights papers by how many authors share them while keeping the index bounded. Together these indices give simple, comparable summaries of co-authorship intensity that have documented the long-term rise of team science across nearly every field, and they remain standard descriptive tools in scientometrics, library science, and research-policy studies of collaboration.