CWTS Leiden Ranking

Paul Wouters p.f.wouters at CWTS.LEIDENUNIV.NL
Wed Apr 30 08:30:20 EDT 2014

*CWTS Press Release Leiden Ranking 2014*

Leiden, The Netherlands, April 30, 2014

*Rockefeller University ranked first after expansion of CWTS Leiden Ranking*

Rockefeller University, a private university located in New York, is ranked
first in the CWTS Leiden Ranking 2014 ( Of the 750
universities included in the ranking, Rockefeller has the highest
percentage of frequently cited publications. Rockefeller is a relatively
small university in terms of publication output. Because of this, it was
not included in previous editions of the Leiden Ranking. In the 2014
edition, the number of universities included in the ranking has been
increased from 500 to 750 and a number of smaller institutions, among which
Rockefeller, have been added to the ranking. Rockefeller is ranked above
MIT, Harvard, UC Berkeley, and Stanford, which occupy positions 2 to 5 in
the ranking. Like in earlier years, the top 50 universities with the
highest percentage of frequently cited publications is strongly dominated
by US institutions, with just a few non-US institutions. These non-US
institutions are from the UK, Switzerland, and Israel.

*Expanded ranking offers improved global coverage of universities*

The CWTS Leiden Ranking 2014 includes the 750 universities worldwide with
the largest number of publications in international scientific journals
covered by the Web of Science database. These universities are located in
49 different countries. Compared with last year’s ranking, Estonia,
Hungary, Lebanon, Slovakia, and Tunisia are new in the 2014 edition. With
166 universities, the US contributes most universities to the Leiden
Ranking. China is ranked second, with 83 universities. Europe as a whole
contributes 288 universities. Brazil, India, and Iran, which are often seen
as upcoming nations in science, each contribute around 15 universities. The
citation impact of these universities is low, usually far below the
worldwide average level. Russia contributes just one university to the 2014
edition of the Leiden Ranking.

*Advanced methodology*

The CWTS Leiden Ranking differs from other university rankings by focusing
exclusively on measuring citation impact and scientific collaboration. The
bibliometric methodology of the Leiden Ranking is considerably more
advanced compared with other rankings. For instance, publications outside
the international scientific literature (e.g., in non-English language
journals or in popular magazines) are excluded because they could distort
citation statistics. Publications that have been withdrawn, for instance
because of scientific misconduct, are excluded as well. The Leiden Ranking
also carefully corrects for differences between scientific fields in
citation and collaboration practices. Other rankings do not perform such
corrections or they do so in a less accurate way. Because of this, these
rankings may be biased in favor of universities active in certain fields of
science. In addition to overall statistics, the Leiden Ranking also
provides statistics at the level of seven broad fields of science. These
fields have been defined algorithmically in a unique bottom-up fashion
based on millions of citation relations between publications in the Web of
Science database.

*Comparison with other university rankings*

Compared with other global university rankings, the world top in the CWTS
Leiden Ranking is dominated more heavily by the US. This is caused by the
strict focus of the Leiden Ranking on citation impact. Both the Times
Higher Education ranking and the Shanghai Ranking combine other aspects of
the performance of universities in a composite indicator, such as teaching
and attracting external funding. The top list is therefore more diverse in
these rankings, even though the US is still dominant. British universities
have a stronger position in the Times Higher Education ranking due to the
reputation of established universities which is measured through a survey.
In the Shanghai Ranking, larger and older universities are advantaged over
smaller and more recently established universities. Through its strict
focus on the citation impact of recent research, the Leiden Ranking is less
influenced by performance in the distant past than other global rankings.

*Rankings require careful interpretation*

Despite the advanced methodology of the CWTS Leiden Ranking, a careful
interpretation of the ranking remains essential. For instance, Rockefeller
University has the highest percentage of frequently cited publications, but
looking at the absolute number of frequently cited publications Rockefeller
turns out to be a relatively small player that appears around position 300
in the ranking. The university with the largest absolute number of
frequently cited publications is Harvard, which has more than twice as many
frequently cited publications as Stanford, the university that is ranked
second in absolute terms. Furthermore, like any ranking, the Leiden Ranking
is sensitive to all kinds of methodological choices. Improvements that have
been made to the methodology of the 2014 edition of the ranking have for
instance caused many Chinese universities to decrease in the ranking.
Finally, it is important to be aware that citation impact does not
necessarily coincide with actual scientific impact. There are for instance
indications that the citation impact of some universities is influenced by
‘cartels’ of scientists who frequently cite each other for inappropriate

*Contact information*

 *Paul Wouters, director of CWTS and professor of Scientometrics*

Phone: +31 71 5273909 (secretariat)

E-mail: p.f.wouters at

*Ludo Waltman, leader of the CWTS Advanced Bibliometric Methods working

Phone: +31 71 5275806

E-mail: waltmanlr at
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