Garfield's Law of Concentration
Also known as: Law of Concentration, Core Journal Concentration, Garfield Concentration Law
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.
Key highlights
- Provides the empirical and conceptual justification for selective, citation-based journal indexing covering most of science with a small core.
- Unifies within-field scattering (Bradford) and across-science concentration through the insight that fields' tails are other fields' cores.
- Descriptive and data-grounded, derived directly from large-scale citation counts rather than assumption.
- Practical for library collection management and for prioritizing which journals to monitor or acquire.
Intuition
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How it works
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When to use it
Use Garfield's law of concentration when you need to justify or design a selective, citation-based view of the literature: building or evaluating a citation index or core journal collection, planning library acquisitions under budget constraints, or arguing that monitoring a manageable set of high-impact journals can cover most of science. It is appropriate when you have citation data linking citing works to source journals across many fields and want a descriptive account of how coverage concentrates. The law is less suitable as a precise predictive model — it is an empirical regularity with fuzzy core boundaries — and it can understate the importance of small, specialized, or non-English journals in particular niches, so it should not be used to dismiss the long tail in fields where local or emerging venues carry distinctive content.
Strengths & limitations
- Provides the empirical and conceptual justification for selective, citation-based journal indexing covering most of science with a small core.
- Unifies within-field scattering (Bradford) and across-science concentration through the insight that fields' tails are other fields' cores.
- Descriptive and data-grounded, derived directly from large-scale citation counts rather than assumption.
- Practical for library collection management and for prioritizing which journals to monitor or acquire.
- The core size (roughly 500 to 1,000 journals) is an approximate, time- and database-dependent figure, not a sharp threshold.
- Concentration measured from a particular index inherits that index's coverage biases, which historically underrepresent non-English and regional journals.
- It is a descriptive regularity, not a mechanism, and it can be invoked to over-justify excluding the long tail.
- Field boundaries and what counts as the 'core' are fuzzy, and highly specialized fields may have important venues outside any general core.
Common pitfalls
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Applications
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Frequently asked
How is the law of concentration related to Bradford's law of scattering?
Bradford's law describes scattering within a single subject: articles on a topic are spread across a small core of journals plus successively larger zones of less productive ones. Garfield's law of concentration is its science-wide corollary. He observed that the scattered tail of any one field consists largely of the core journals of other fields, so when all fields are combined their cores overlap and collapse into one small multidisciplinary core. Concentration across science and scattering within a field are thus two views of the same structure.
How large is the multidisciplinary core?
Garfield estimated that a core of roughly 500 to 1,000 journals accounts for the great majority of all citations across science. This figure is approximate and depends on the time period, the citation database, and where one draws the line for 'core'; as science has grown the absolute numbers have shifted. The enduring point is qualitative: the core is small relative to the tens of thousands of journals published, which is what makes selective citation indexing feasible.
Does the law mean small or specialized journals do not matter?
No. The law describes where citations concentrate, not where all value lies. Specialized, regional, and non-English journals can carry content that is important locally or in emerging niches even if they sit in the long tail of global citation counts, and citation databases have historically underrepresented them. The concentration law justifies efficient broad coverage with a core, but using it to dismiss the tail entirely misreads it and risks systematic blind spots.
Sources
- 1.Garfield, E. (1972). Citation analysis as a tool in journal evaluation. Science, 178(4060), 471-479.
- 2.Bradford, S. C. (1934). Sources of information on specific subjects. Engineering: An Illustrated Weekly Journal, 137, 85-86.
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Cite this page
ScholarGate. (2026, June 23). Garfield's Law of Concentration. ScholarGate. https://scholargate.app/bibliometrics/garfields-law-of-concentration