Essential
Science IndicatorsSM is a compilation of
statistical information (publication, citation, and cites-per-paper
counts) for scientists, institutions, countries, and journals. It is
based on 10 years of Thomson Reuters data. The Essential Science
Indicators
Data
Information Pages will help you understand how Essential
Science Indicators works using counting methods for articles
and citations, time periods for counts, types of items counted,
journals included, citation thresholds, name conflation, name
variations, and rank orderings.
Essential Science Indicators, accessible by subscribers
through a Web interface, is updated every two months. During the course
of a year, the data series presented covers 10 years plus a successive
number of recent two-month periods, eventually reaching an 11-year time
span. At the end of the year, the compilation reverts to a 10-year data
set, dropping off the oldest year of the series.
View the latest
version information, along with the 2007 and 2008 update
schedule.
STATISTICS
Here are some rough statistics on the magnitude of the Thomson
Reuters data file that is processed to obtain the information included
in Essential Science Indicators:
In a recent 10-year period
Thomson Reuters recorded about 9 million
articles, notes, and reviews, published in roughly 10,000 indexed
journals. Essential Science Indicators categorizes these
journals into 22 broad
disciplines. Each journal is assigned to one of the 22
disciplines (See complete
journal list for
Essential Science Indicators). Similarly, Essential
Science Indicators then assigns each paper to a
discipline—and only one discipline—based on the journal
in which it appears. In the case of multidisciplinary journals,
special processing is carried out to assign individual papers to
fields based on the predominate field of the papers' citations and
references. The number of citations received by these 9 million
items, (originating, of course, from the same Thomson
Reuters-indexed journal literature), is roughly 85 million. These
are the footnotes, or references, that appear in the journal
articles. The Thomson Reuters data file is unique in capturing these
so-called cited references (see also:
Classification
of Papers in Multidisciplinary Journals).
Essential Science Indicators identifies the "essential core"
of journal articles, scientists, institutions, countries, and journals
from this large data corpus by setting selection criteria (a certain
number of citations) for each of the disciplines. These thresholds, set
to select some constant fraction of items, are described in an
accompanying document
(citation thresholds).
For example, for highly cited papers, Essential Science
Indicators selects the top 1% of articles by total citations in
each annual cohort from each of the 22 disciplines. Highly cited papers
in Essential Science Indicators total about 90,000 items.
Essential Science Indicators also identifies "hot papers,"
which date from the last two years and which have received an unusually
high number of citations during the most recent two-month period. About
1,800 hot papers are selected, representing the top 0.1% in the
two-year period.
Of the roughly 4 million scientists' names appearing in the 10 years of
Thomson Reuters data surveyed, about 60,000 are listed in Essential
Science Indicators. This represents the top 1% of authors in terms
of total citations in each of the disciplines over the 10 years. Each
scientist name appears, on average, in 1.3 disciplines. About 700,000
institutional affiliations are scanned in the 10-year data file, and
about 4,000 of these are selected for Essential Science
Indicators, also representing the top 1% in each discipline
(unification of institutional names is undertaken to obtain more
accurate statistics). Each of the selected institutions appears, on
average, in 3.1 disciplines.
For countries, about 150 are selected out of about 200 scanned, and for
journals about 5,000 of the 10,000, both representing the top 50% by
discipline and total citations over the 10-year period. As noted
before, journals are assigned uniquely to only one discipline (with the
exception of multidisciplinary journals), but each country appears on
average in about 13 disciplines.
UNDERSTANDING CORE
DATA
Below are very useful links (Essential Science) to help you understand
how the Essential Science Indicators works using counting
methods for articles and citations, time periods for counts, types of
items counted, journals included, citation thresholds, name conflation,
name variations, and rank orderings for:
Should you have further questions, please
contact us.
