Essential Science IndicatorsSM
Understanding Core Data - Countries
Countries vary in their level of scientific effort as measured by
publication and citation activity. The distribution of effort is
uneven, and dominated by the developed countries. The level of activity
is roughly correlated with national GNP or other measures of economic
output. Comparing countries on a citations per paper basis can help
correct for size (output) differences.
Counting method for articles and citations:
Country counts are based on the institutional affiliations given on
published papers. A paper is attributed to a country if the paper
carries at least one address from that country. All addresses are
considered, not only the address listed first. If a country appears
more than once on a paper, it is counted only once for that
country. All unique countries on a paper are credited equally for
the paper. All citations received by a paper are credited equally
to all the countries on the cited paper. No restrictions are made
on the citing items in compiling the citation counts, other than
that they are recorded from Clarivate Analytics-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 Analytics 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.
Essential Science Indicators counts are based on an
Clarivate Analytics 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 the individual
scientist, institution, or country.
Countries selected for listing in Essential Science
Indicators must meet a cumulative citation count threshold for
the 10+ year period. The thresholds are set separately for each
field. More information about the actual
thresholds used in
Essential Science Indicators.
The absence of a country's name in Essential Science
Indicators means the country did not meet the citation
threshold in any field.
Country Name changes and unification:
Country names have been unified to reflect name or country
boundaries that have changed. For example, West Germany and East
Germany have been unified to Germany for the 10-year period. The
United Kingdom has been treated as a single country, rather than
having separate entries for England, Scotland, Wales, and Northern
Ireland. Data on some of the newly independent states of the former
Soviet Union are available only after 1995, and for some eastern
European countries since 1993.
Countries 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 country output.
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