MEASURING COMMUNICATION
IN SCIENCE
OPPORTUNITIES AND LIMITATIONS OF
BIBLIOMETRIC METHODS
Wolfgang Glänzel and Koenraad Debackere
SooS, Leuven, Belgium
STRUCTURE OF THE PRESENTATION
Introduction
1. Structure of Bibliometrics
2. Data sources of bibliometric research and technology
3. Elements, units and measures of bibliometric
research
4. Citations and Self-citations
5. “Against absolute methods”
6. Journal Impact Factor
7. Distorted behaviour based on policy use and misuse
of bibliometric data
Conclusions
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INTRODUCTION
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Introduction
What is bibliometrics?
The terms bibliometrics and scientometrics were almost
simultaneously introduced by Pritchard and by Nalimov &
Mulchenko in 1969.
According to Pritchard bibliometrics is
“the application of mathematical and statistical
methods to books and other media of
communication”.
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Introduction
Nalimov and Mulchenko defined scientometrics as
“the application of those quantitative methods which
are dealing with the analysis of science viewed as an
information process”.
The two terms have become almost synonyms;
nowadays, the field informetrics (Gorkova, 1988)
stands for a more general subfield of information
science dealing with mathematical-statistical analysis
of communication processes in science.
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Introduction
Present-day use of bibliometrics
• Bibliometrics has evolved to a standard tool of
science policy and research management.
• A vast array of indicators to measure and to map
research activity and its progress is available.
• Science indicators relying on comprehensive
publication and citation statistics and other, more
sophisticated bibliometric techniques, are used in
science policy and research management.
• A growing, often controversial, policy interest to use
bibliometric techniques in measurements of
research productivity and efficiency.
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Introduction
Common misbeliefs on bibliometrics
• Main task of bibliometrics should be the expeditious
issuing of “prompt” and “comprehensible” indicators
for science policy and research management.
• Research on bibliometric methodology is
unnecessary; instead bibliometricians should
elaborate guidelines explaining the use of their
indicators.
• Bibliometrics might be reduced to simple counting
activities in order to replace/supplement qualitative
assessment by quantitative indicators and to set
publication output off against funding.
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Introduction
Facts about bibliometrics
• Bibliometrics is a powerful, multifaceted endeavour
encompassing subareas such as structural, dynamic
and evaluative scientometrics.
- Structural scientometrics came up with results
like the re-mapping of the epistemological
structure of science.
- Dynamic scientometrics constructed
sophisticated models of scientific growth,
obsolescence, citation processes, etc.
- Evaluative scientometrics developed arrays of
indicators to be used to characterise research
performance at different levels of aggregation.
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Introduction
What is bibliometrics dealing with and what can
bibliometrics not be responsible for?
• Bibliometrics can be used to develop and provide
tools to be applied to research evaluation, but is not
designed to evaluate research results.
• Bibliometrics does not aim at replacing qualitative
methods by quantitative approaches.
• Consequently, bibliometrics is not designed to correct
or even substitute peer reviews or evaluation by
experts but qualitative and quantitative methods in
science studies should complement each other.
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1. STRUCTURE OF BIBLIOMETRICS
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1.
Structure of Bibliometrics
The three “components” of present-day bibliometrics
according to its three main target-groups
Bibliometrics for bibliometricians (Methodology)
This is the domain of bibliometric “basic research”.
Bibliometrics for scientific disciplines (Scientific information)
A large but also the most diverse interest-group in bibliometrics.
Due to the scientists’ primary scientific orientation, their interests are
strongly related to their speciality. Here we also find joint borderland
with quantitative aspects of information retrieval.
Bibliometrics for science policy and management (Science policy)
At present the most important topic in the field. Here the national,
regional, and institutional structures of science and their comparative
presentation are in the foreground.
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1.
Structure of Bibliometrics
Links of bibliometrics with related research fields and application services
Science policy
Research management
Scientific information
Librarianship
Services for
Research in
Economics
Sociology of science
History of science
applied
Library and
Information Science
Scientometrics
basic
Life sciences
Informetrics
Mathematics/Physics
Webometrics
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2. DATA SOURCES OF BIBLIOMETRIC
RESEARCH AND TECHNOLOGY
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2.
Sources of Bibliometrics
Data sources of bibliometric research and technology
Data sources of bibliometrics are bibliographies and
bibliographic databases. Large scale analyses can only be
based on bibliographic databases.
Prominent specialised databases are, e.g., Medline, Chemical
Abstracts, INSPEC and Mathematical Reviews in the sciences
and, e.g., Econlit, Sociological Abstracts and Humanities
Abstracts in the social sciences and humanities.
 Disadvantage: Lack of reference literature, incomplete
address recording
The databases of the Institute for Scientific Information
(Thomson - ISI), above all, the Science Citation Index
(Expanded) have become the most generally accepted
source of bibliometrics.
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2.
Sources of Bibliometrics
Although, there are several objections against the journal
coverage and the data processing policy of the ISI in
preparing the SCI, its unique features are basic
requirements of bibliometric technology. Among these
features we have
•
•
•
Multidisciplinarity
Selectiveness
Completeness of addresses
•
•
Full coverage
Bibliographical references
 Disadvantage: no individual subject classification for
papers available.
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2.
Sources of Bibliometrics
ProceedingsSM is available in two editions (Science &
Technology and Social Sciences & Humanities) covering
about 2,000,000 papers from over 60,000 conferences
since 1990.
Non-serial literature (except for proceedings) such as
monographs and books is not indexed in these ISI
databases.
Since non-serial literature is an important conveyor of
information in the social sciences and humanities, journal
based data-sources are accepted by scientists only with
certain reservations.
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3. ELEMENTS, UNITS AND MEASURES OF
BIBLIOMETRIC RESEARCH
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3.
Elements of Bibliometrics
Elements, units and measures of bibliometric research
Basic units in bibliometrics are usually not further subdivided.
These form the elements of bibliometric analyses. Elements are,
e.g., publications, (co-)authors, references and citations.
Publications can be assigned to the journals in which they
appeared, through the corporate addresses of their authors to
institutions or countries, references and citations to subject
categories, and so on.
Units are specific sets of elements, e.g., journals, subject
categories, institutions, regions and countries to which elements
can – not necessarily uniquely – be assigned. The clear definition
of the assignment – or in mathematical parlance – of mappings
between elements and units allows the application of
mathematical models.
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3.
Elements of Bibliometrics
Publication activity and authorship
Publication activity is influenced by several factors. At the micro
level, we can distinguish the following four factors.
1.
the subject matter
2.
the author’s age
3.
the author’s social status
4.
the observation period
The publication activity in theoretical fields (e.g., mathematics)
and in engineering is lower than in experimental fields or in the
life sciences.
Cross-field comparison – without appropriate normalisation –
would not be valid. This applies above all to comparative
analyses at the meso level (universities and departments).
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3.
Elements of Bibliometrics
Can scientific collaboration be measured through
co-authorship?
•Laudel (2001) (micro study): A large share of persons involved in
the preparation of a scientific paper does thus not appear either
as co-author or as a sub-author. Katz & Martin (1997) argue that
co-authorship is no more than a partial indicator of collaboration.
•Intensifying collaboration, however, goes with growing coauthorship (Patel, 1973). There is a positive correlation between
collaboration and co-authorship at the level of individual actors,
too.
•The phenomenon described by Laudel and Katz & Martin rather
applies to intramural collaboration. Extramural collaboration,
above all international collaboration, is usually well
acknowledged.
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4. CITATIONS AND SELF-CITATIONS
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4.
Citations and Self-citations
The notion of citations in information science and
bibliometrics
Citations became a widely used measure of the impact of
scientific publications.
Cozzens: “Citation is only secondarily a reward system.
Primarily, it is rhetorical-part of persuasively arguing for the
knowledge claims of the citing document.”
L. C. Smith: "citations are signposts left behind after
information has been utilized".
Cronin: Citations are "frozen footprints in the landscape of
scholarly achievement … which bear witness to the passage
of ideas“.
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4.
Citations and Self-citations
Glänzel and Schoepflin: Citations are “one important form of use
of scientific information within the framework of documented
science communication,” Although citations cannot describe
the totality of the reception process, they give, “a formalised
account of the information use and can be taken as a strong
indicator of reception at this level.”
Westney: “Despite its flaws, citation analysis has demonstrated
its reliability and usefulness as a tool for ranking and evaluating
scholars and their publications. No other methodology permits
such precise identification of the individuals who have
influenced thought, theory, and practice in world science and
technology.”
Garfield and Weinstock have listed 15 different reasons for giving
citations to others’ work.
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4.
Citations and self-citations
The process of re-interpreting the notion of citation and its
consequences
interpretation
citation
Bibliometrics/
Information science
Signpost of information use
repercussion
re-interpretation
(possible distortion of
citation behaviour)
Research evaluation/
Science policy
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uncitedness: unused information
frequent cite: good reception
self-cite: part of scient. communication
Rewarding system/
Quality measure
uncitedness: low quality
frequent cite: high quality
self-cite: manipulation of impact
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5. “AGAINST ABSOLUTE METHODS”
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“Against absolute methods”
5.
Factors influencing citation impact
Citation impact is mainly influenced by the following five factors
that are analogously to the case of publication activity at higher
levels of aggregation practically quite inseparable.
1. the subject matter and within a subject, the “level of
abstraction”
2. the paper’s age
3. the paper’s “social status” (through authors and journal)
4. the document type
5. the observation period (”citation window”)
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“Against absolute methods”
5.
Complexity of influences and biases in calculating
citation impact measures
Mean citation rate of two journals in time as a function of time
(source year: 1980)
Citation
window
1980-80
1980-81
1980-82
1980-85
1980-89
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Mean citation rate
ASR
LANCET
0.2
0.6
1.8
2.4
4.3
4.5
12.1
9.7
20.9
14.0
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“Against absolute methods”
5.
Impact of different document types
”3-year impact measure” for selected journals by document types
(source: 1995/96)
# Journal
1 SCIENCE
Total
32.86
2 NATURE
3 LANCET
Impact Factor
Articles
Reviews
Letters
42.30
145.35
0.41
32.88
49.73
96.07
3.93
5.25
17.55
14.68
1.99
4 CELL
75.68
74.82
78.63
75.64
5 ANGEW CHEM INT ED
11.01
9.37
32.03
19.00
6 J ACQ IMMUN DEFIC SYND HUM R
4.05
4.64
39.00
1.04
7 INT J RAD ONCOL BIOL PHY
3.52
4.15
35.00
0.37
8 J PHYS CONDENS MATTER
2.72
2.47
9.57
3.99
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“Against absolute methods”
5.
Influence of subject characteristics
Mean citation rate of subfields
(source: 1996, citation window: 1996-1998)
Mechanical, civil and other engineering
Mathematics
Analytical chemistry
Solid state physics
Neurosciences
1.12
1.46
3.00
3.06
4.54
Citation measures are thus – without normalisation – not
appropriate for cross-field comparisons.
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“Against absolute methods”
5.
 The only possible way to compensate for
the subject-specific characteristics is an
appropriate normalisation and the
application of exactly the same
underlying publication period and
citation window to all units under study.
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“Against absolute methods”
5.
Citation indicators can be normalised using a reference standard
based on journals or subjects in which the papers under study
have been published.
Problem: Subject assignament is not unique.
The Relative Citation Rate (RCR) introduced by Schubert et al.
in 1983 gauges observed citation rates of the papers against the
standards set by the specific journals. It has largely been
applied to comparative macro and meso studies since. A version
of this relative measure, namely, CPP/JCSm, where JCSm
denotes the mean Journal Citation Score is used at CWTS.
The Normalised Mean Citation Rate (NMCR) introduced by
Braun and Glänzel in 1993 normalises observed citation rates
by weighted average of the mean citation rates of subfields.
A similar measure (CPP/FCSm, FCSm being the mean Field
Citation Score) is used at CWTS.
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6. JOURNAL IMPACT FACTOR
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6.
Journal Impact Factor
On the role of the Impact Factor
• The Garfield ISI Impact Factor (IF) represents a
paradigm in bibliometric/information science research.
• The IF is used frequently and has obtained a very strong
‘market’ position.
• From the mathematical viewpoint, the IF is the mean
value, i.e., an arithmetic mean of citations in a particular
(citing) year to a particular set of articles published in a
particular journal one or two years earlier.
• The Impact Factor has become perhaps the most
popular bibliometric product used in bibliometrics and
outside the scientific community.
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6.
Journal Impact Factor
Problems in using the ISI Impact Factors
•
The strengths of the Impact Factor lies first of all in the
comprehensibility, stability and seeming reproducibility, but some
flaws have provoked critical and controversial discussions about
its correctness and use.
•
The above-mentioned popularity involves also dangers. The use
of impact factors ranges from well-documented and methodically
sound applications to rather ‘grey’ applications as background
information for scientific journalism or in the context of refereeing
procedures. Impact factors are sometimes used even as
substitutes for missing citation data.
•
Although it is difficult to theoretically define the concept of
(journal) impact, there is a wide spread belief that the ISI Impact
Factor is affected or ‘disturbed’ by factors that have nothing to do
with (journal) impact.
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6.
Journal Impact Factor
•
Being a statistical mean, the IF should be size-independent.
Large journals might, however, often have a higher visibility.
•
The robustness, comprehensibility and methodological
reproducibility of the ISI journal Impact Factor is contrasted by
methodological shortcomings and its technical irreproducibility.
•
It became quite tempting to apply the impact factor as a universal
bibliometric measure. This is certainly one source of possible
uninformed use.
•
Methodological improvements in combination with
complementary measures and an appropriate documentation
may help to overcome limitations described above.
•
The question of reproducibility can thus at least partially be
solved for those who have access to the bibliographic databases
and the technology to produce journal indicators.
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6.
Journal Impact Factor
Visibility vs. publication targeting vs. citation impact
Publication in a high-IF journal might guarantee excellent visibility, but
not automatically imply high citation rates, too.
In several fields, targeting, i.e., reaching the desired audience is more
important than publishing in high-impact journals (e.g., in clinical
medicine, mathematics).
The latter observation substantiates that research may have other
impact than citations. In order to gain new insight in the utility of
biomedical research Grant Lewison studied citations from clinical
guidelines, textbooks, government policy documents, international or
national regulations and newspaper articles. Moreover, publications in
technical sciences and clinical medicine might find practical application
that cannot be measured through citations.
 Citations and, above all, the IF do not measure all
aspects of impact published research results might have.
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6.
Journal Impact Factor
The myth of delayed recognition
An often-heard argument on limitations of citation-based
indicators is that important publications are often not cited in the
beginning, and only become recognised in a time that is beyond
the standard citation windows used in most bibliometric studies.
Studies by Glänzel at al. and Glänzel & Garfield in 2004 have
shown that the chance that a paper, uncited for three to five
years after publication, will ever be cited is quite low, even in
slowly aging fields such as mathematics. The citation impact of
papers not cited initially usually remains low even 15 to 20 years
later.
The potential number of delayed recognition papers is extremely
small. A statistically marginal share of 1.3 per 10,000 papers
published in 1980 were "neglected" at first, and then, belatedly,
received relatively high citational recognition.
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7. DISTORTED BEHAVIOUR BASED ON
POLICY USE AND MISUSE OF
BIBLIOMETRIC DATA
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7.
Distorted behaviour
Distorted behaviour based on policy use and misuse of
bibliometric data
An additional issue concerns the changes in the publication,
citation and collaboration behaviour of scientists (both
positive and negative) that the consistent policy use of
bibliometric indicators might potentially induce.
Studies on the problem choice behaviour of academic
scientists have revealed that both cognitive and social
influences determine the manner in which scientists go about
choosing the problems they work on (Debackere and Rappa
1994). Hence the issue should be raised to what extent the
policy use of bibliometrics might or could affect this behaviour.
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7.
Distorted behaviour
The problem of inappropriate use ranges from uninformed use,
over selecting and collecting ‘most advantageous’ indicators to
the obvious and deliberate misuse of data.
Uninformed use and misuse are not always beyond the
responsibility of bibliometricians. Unfortunately, bibliometricians
do not always resist the temptation to follow popular, even
populist, trends in order to meet the expectations of the
customers.
Clearly, any kind of uninformed use or misuse of bibliometric
results involves the danger of bringing bibliometric research
itself into disrepute.
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7.
Distorted behaviour
Uninformed use
• incorrect presentation, interpretation of bibliometric
indicators or their use in an inappropriate context caused
by insufficient knowledge of methodology, background and
data sources
• generalisation (induction) of special cases or of results
obtained at lower levels of aggregation
Misuse
• intentionally incorrect presentation, interpretation of
bibliometric indicators or their deliberate use in
inappropriate context
• tendentious application of biases
• tendentious choice of (incompatible) indicators
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7.
Distorted behaviour
But even correct use might have undesired consequences.
Example: Re-interpreting underlying contexts such as the notion
of citation (cf. Section 4) shows author self-citations in an
unfavourable light. Authors might thus be urged avoiding selfcitations – a clear intervention into the mechanism of scientific
communication.
Less obvious repercussions might be observed when bibliometric
tools are used in decision-making in science policy and research
management and the scientific community recognises the
feedback in terms of their funding.
Butler (2004) has shown on the example of Australia what might
happen when funding is linked to publication counts. She found
that the publications component of the Composite Index has
stimulated an increased publication activity in the lower impact
journals.
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7.
Distorted behaviour
Schematic visualisation of the feedback of policy use of
bibliometrics on the scientific community
Bibliometrics
Scientific community
Publication & citation
behaviour
Science policy &
Research management
Funding &
Promotion
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7.
Distorted behaviour
Possible positive effects
Scientists might recognise that scientific collaboration and
publishing in high-impact or even top journals pays. Also their
publication activity might be stimulated.
Possible negative effects
Exaggerated collaboration, even trends towards hyperauthorship, inflating publication output by splitting up
publications to sequences, inflating citation impact by selfcitations and forming citation cliques, etc. Trend towards
replacing quality and recognition by visibility at any price or
towards preferring journals as publication channels in social
sciences and humanities might be among these effects.
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CONCLUSIONS
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Conclusions
• The future will show in how far these negative effects will
become reality. Empirical monitoring and examination of
hypothetical biases will be worthwhile.
• Similar trends could already be observed far before the time of
bibliometrics:
Striving after visibility and reputation is part of human nature.
Most negative effects will probably be hindered or prevented
through the natural competition and peer review among
researchers.
• The only negative feedback from policy use and misuse of
bibliometric data might on the long run results in general
‘inflationary values’ described, e.g., by Cronin (2001) and
Persson et al. (2003). Bibliometricians have the tools to
normalise and standardise indicators under such conditions,
and are thus able to cope with this problem, too.
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