Essential Science IndicatorsSMData Information:
Understanding Core Data - Journals
Journals also vary widely in prestige, influence, and impact, and this
is reflected in the citation counts to a journal. Essential Science
Indicators provides a long-term citation ranking for journals. A
comparison with short-term citation behavior can be made by consulting
the Journal Citation Reports (JCR) product published by ISI.
Counting method for papers and citations:
Papers are attributed to their journal of publication. All
citations received by a paper in a journal are credited to the
journal of the cited paper. No restrictions are made on the citing
items in compiling the citation counts, other than that they are
recorded from Clarivate-indexed journals only.
Time period for counts (cites, papers, cites per
The time period for Essential Science Indicators counts is
10 years, plus partial-year counts for the current year (data is
updated six times a year). This means that any papers in the 10+
year period can be cited by any items in that same period. Thomson
Reuters database years (the actual years when items are entered
into the Clarivate database, which is not necessarily the
publication year) are used to define the time periods.
Types of items counted:
Papers are defined as regular scientific articles, review articles,
proceedings papers, and research notes. Letters to the editor,
correction notices, and abstracts are not counted. Only Thomson
Reuters-indexed journal articles or papers are counted.
Journals included for ranking are drawn from the Essential
Science Indicators journal set (see complete
journal list for
Essential Science Indicators) categorized into
22 broad fields.
Fields are defined by a unique grouping of journals, with no
journal being assigned to more than one field. The
Multidisciplinary field contains journals such as Science
and Nature which in an article level
would be assigned to specific fields. This should be taken into
account when analyzing the field ranking of an individual
scientist, institution, or country.
Journals selected for listing in Essential Science
Indicators must meet a cumulative citation count threshold for
the 10+ year period. More information about the actual
thresholds used in
Essential Science Indicators.
The absence of a journal name in Essential Science
Indicators means the journal did not meet the citation
threshold for the field to which it has been assigned.
Journal Name variations and unification:
Journal names have been unified to reflect name changes or journal
mergers over the ten-year period.
Journals in the rankings are numbered from 1 to N, depending on the
ranking option selected, with no repeated ranks for ties (ties are
then ranked alphabetically). Ranking options include citations,
papers, citations per paper, and alphabetic. The citations per
paper ranking normalizes to some degree for journal size.