Misconduct accounts for the majority of retracted
Ferric C. Fang
, R. Grant Steen
, and Arturo Casadevall
Laboratory Medicine and
Microbiology, University of Washington School of Medicine, Seattle, WA 98195;
Communications Consultants, Chapel Hill, NC 27517; and
Department of Microbiology and Immunology, Albert Einstein College of Medicine, Bronx, NY 10461
Edited by Thomas Shenk, Princeton University, Princeton, NJ, and approved September 6, 2012 (received for review July 18, 2012)
A detailed review of all 2,047 biomedical and life-science research
articles indexed by PubMed as retracted on May 3, 2012 revealed
that only 21.3% of retractions were attributable to error. In contrast,
67.4% of retractions were attributable to misconduct, including
fraud or suspected fraud (43.4%), duplicate publication (14.2%), and
plagiarism (9.8%). Incomplete, uninformative or misleading retrac-
tion announcements have led to a previous underestimation of the
role of fraud in the ongoing retraction epidemic. The percentage of
scientiﬁc articles retracted because of fraud has increased ∼10-fold
since 1975. Retractions exhibit distinctive temporal and geographic
patterns that may reveal underlying causes.
The number and frequency of retracted publications are im-
portant indicators of the health of the scientiﬁc enterprise,
because retracted articles represent unequivocal evidence of
project failure, irrespective of the cause. Hence, retractions are
worthy of rigorous and systematic study. The retraction of ﬂawed
publications corrects the scientiﬁc literature and also provides
insights into the scientiﬁc process. However, the rising frequency
of retractions has recently elicited concern (1, 2). Studies of se-
lected retracted articles have suggested that error is more com-
mon than fraud as a cause of retraction (3–5) and that rates of
retraction correlate with journal-impact factor (6). We undertook
a comprehensive analysis of all retracted articles indexed by
PubMed to ascertain the validity of the earlier ﬁndings. Retracted
articles were classiﬁed according to whether the cause of re-
traction was documented fraud (data falsiﬁcation or fabrication),
suspected fraud, plagiarism, duplicate publication, error, un-
known, or other reasons (e.g., journal error, authorship dispute).
Causes of Retraction. PubMed references more than 25 million
articles relating primarily to biomedical research published since
the 1940s. A comprehensive search of the PubMed database in
May 2012 identiﬁed 2,047 retracted articles, with the earliest
retracted article published in 1973 and retracted in 1977. Hence,
retraction is a relatively recent development in the biomedical
scientiﬁc literature, although retractable offenses are not neces-
sarily new. To understand the reasons for retraction, we consulted
reports from the Ofﬁce of Research Integrity and other published
resources (7, 8), in addition to the retraction announcements in
scientiﬁc journals. Use of these additional sources of information
resulted in the reclassiﬁcation of 118 of 742 (15.9%) retractions in
an earlier study (4) from error to fraud. A list of 158 articles for
which the cause of retraction was reclassiﬁed because of consul-
tation of secondary sources is provided in Table S1. For example,
a retraction announcement in Biochemical and Biophysical Re-
search Communications reported that “results were derived from
experiments that were found to have ﬂaws in methodological
execution and data analysis,”giving the impression of error (9).
However, an investigation of this article conducted by Harvard
University and reported to the Ofﬁce of Research Integrity in-
dicated that “many instances of data fabrication and falsiﬁca-
tion were found”(10). In another example, a retraction notice
published by the authors of a manuscript in the Journal of Cell
Biology stated that “In follow-up experiments ...wehave shown
that the lack of FOXO1a expression reported in ﬁgure 1 is not
correct”(11). A subsequent report from the Ofﬁce of Research
Integrity states that the ﬁrst author committed “research mis-
conduct by knowingly and intentionally falsely reporting . . . that
FOXO1a was not expressed ...byselecting a speciﬁc FOXO1a
immunoblot to show the desired result”(12). In contrast to earlier
studies, we found that the majority of retracted articles were
retracted because of some form of misconduct, with only 21.3%
retracted because of error. The most common reason for re-
traction was fraud or suspected fraud (43.4%), with additional
articles retracted because of duplicate publication (14.2%) or
plagiarism (9.8%). Miscellaneous reasons or unknown causes
accounted for the remainder. Thus, for articles in which the
reason for retraction is known, three-quarters were retracted
because of misconduct or suspected misconduct, and only one-
quarter was retracted for error.
Temporal Trends. A marked recent rise in the frequency of re-
traction was conﬁrmed (2, 13), but was not uniform among the
various causes of retraction (Fig. 1A). A discernible rise in re-
tractions because of fraud or error was ﬁrst evident in the 1990s,
with a subsequent dramatic rise in retractions attributable to
fraud occurring during the last decade. A more modest increase
in retractions because of error was observed, and increasing
retractions because of plagiarism and duplicate publication are
a recent phenomenon, seen only since 2005. The recent increase
in retractions for fraud cannot be attributed solely to an increase
in the number of research publications: retractions for fraud or
suspected fraud as a percentage of total articles have increased
nearly 10-fold since 1975 (Fig. 1B).
Geographic Origin and Impact Factor. Retracted articles were auth-
ored in 56 countries, and geographic origin was found to vary
according to the cause for retraction (Fig. 2). The United States,
Germany, Japan, and China accounted for three-quarters of
retractions because of fraud or suspected fraud. China and India
collectively accounted for more cases of plagiarism than the
United States, and duplicate publication exhibited a pattern sim-
ilar to that of plagiarism. The relationship between journal impact
factor and retraction rate was also found to vary with the cause of
retraction. Journal-impact factor showed a highly signiﬁcant cor-
relation with retractions because of fraud or error but not with
those because of plagiarism or duplicate publication (Fig. 3 A–C).
Moreover, the mean impact factors of journals retracting articles
Author contributions: F.C.F., R.G.S., and A.C. designed research, performed research, an-
alyzed data, and wrote the paper.
The authors declare no conﬂict of interest.
This article is a PNAS Direct Submission.
F.C.F., R.G.S., and A.C. contributed equally to this work.
To whom correspondence should be addressed. E-mail: email@example.com.
This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.
October 16, 2012
no. 42 www.pnas.org/cgi/doi/10.1073/pnas.1212247109
because of fraud or error differed signiﬁcantly from that of jour-
nals retracting articles because of plagiarism or duplicate publi-
cation. Accordingly, retractions for fraud or error and retractions
for plagiarism or duplicate publication were encountered in dis-
tinct subsets of journals, with differences in impact factor (Fig. 3D)
and limited overlap (Table 1).
Time-to-Retraction. The time interval between publication and
retraction varied according to the cause of retraction, with arti-
cles retracted because of fraud taking substantially longer to
retract (Table 2). A gradual trend toward increasing time-to-
retraction over time was detected (Fig. 4A). Journal-impact
factor did not correlate with time-to-retraction for manuscripts
retracted because of error, plagiarism, or duplicate publication,
but did exhibit a modest correlation for manuscripts retracted
because of fraud in high-impact journals, which tended to exhibit
a shorter time-to-retraction (Fig. 4B). A small number of authors
were responsible for multiple retractions. Thirty-eight research
groups with greater or equal to ﬁve retractions accounted for
43.9% (n=390) of retractions for fraud or suspected fraud in the
modern biomedical literature (Fig. S1). Nearly all retracted
articles by authors with 10 or more retractions were retracted
because of fraud (Table S2). This ﬁnding is attributable to the
discovery of multiple fraudulent articles during the course of
investigation of a single instance of fraud. For example, the re-
traction of a 2010 Blood article by Sawada et al. (14) was fol-
lowed in rapid succession by the retraction of 30 additional
articles originating from the laboratory of Naoki Mori (Fig. S2).
Citation of Retracted Articles. Previous investigators have found
that many retracted articles continue to be cited as if still valid
work (15, 16), but others have documented an immediate effect
of retraction on citation frequency (17). Although we did not
examine this question comprehensively, we found considerable
variation among the most frequently cited retracted articles
(Table 3). Some retracted articles exhibited a rapid and sus-
tained decline in citations following retraction, but others have
continued to be cited (Fig. S3).
In addition to conﬁrming a recent rise in the incidence of re-
tractions, this study provides a number of additional insights.
Perhaps most signiﬁcantly, we ﬁnd that most retracted articles
result from misconduct, and nearly half of retractions are for
fraud or suspected fraud. In addition to a larger sample size
encompassing all retractions in the biomedical research litera-
ture, this study differs from some previous analyses in the use of
alternative sources of information, such as reports from the Ofﬁce
Fig. 1. (A) Number of retracted articles for speciﬁc causes by year of re-
traction. (B) Percentage of published articles retracted for fraud or suspected
fraud by year of publication.
Fraud or Suspected Fraud
Fig. 2. Country of origin of publications retracted
for fraud or suspected fraud (A), plagiarism (B), or
duplicate publication (C).
Fang et al. PNAS
October 16, 2012
of Research Integrity, Retraction Watch, news media, and other
public records. The US Ofﬁce of Research Integrity was formed
in 1992 and is charged with the oversight of misconduct allega-
tions involving federally sponsored research. As the consider-
ation of secondary sources led to changes in the perceived cause
of retraction in 158 instances (Table S1), we conclude that for
many retractions, the retraction notice is insufﬁcient to ascertain
the true cause of a retraction.
We further note that not all articles suspected of fraud have
been retracted. The Lancet and British Medical Journal expressed
serious reservations about the validity of the Indo-Mediterra-
nean Diet Heart Study after the primary author was unable to
present original records to document ethics review and informed
consent (18, 19), yet the original articles have not been retracted
(20, 21). Several articles authored by Mark Spector when he was
working in the laboratory of Efraim Racker remain in the liter-
ature (22, 23), despite documentation that Spector committed
data fabrication (24). R. K. Chandra was found to have com-
mitted fraud in the performance of clinical trials, but only a single
article was retracted (25), even though considerable evidence was
obtained to suggest that other publications were also fraudulent
(26). Therefore, the current number of articles retracted because
of fraud represents an underestimation of the actual number of
fraudulent articles in the literature.
Although some retraction announcements are speciﬁc and
detailed, many are uninformative or opaque. In 119 instances, no
information regarding the reason for retraction was provided by
the journal. Announcements are often written by the authors of
the retracted article themselves (27), who may be understandably
reluctant to implicate themselves in misconduct. Furthermore, in-
vestigation of suspected misconduct is a lengthy process, and re-
traction notices are frequently made before the full results of in-
vestigations are available. Among 285 investigations concluded by
the Ofﬁce of Research Integrity from 2001 to 2010, the length of
investigation averaged 20.48 mo in duration and ranged up to more
than 9 y (28). Policies regarding retraction announcements vary
widely among journals, and some, such as the Journal of Biological
Chemistry, routinely decline to provide any explanation for re-
traction. These factors have contributed to the systematic un-
derestimation of the role of misconduct and the overestimation of
the role of error in retractions (3, 4), and speak to the need for
uniform standards regarding retraction notices (5).
Differences in the temporal and geographic patterns of re-
traction according to cause (Figs. 1Aand 2) militate against
a simple explanation for retractions. One factor is the increased
detection of misconduct. The ﬁrst discernible increase in
retractions followed the formation of the Ofﬁce of Scientiﬁc
Integrity (the predecessor of the Ofﬁce of Research Integrity)
and passage of the Whistleblower Protection Act in 1989. The
recent increase in the incidence of retractions and the differing
patterns by region (Fig. 2) argue that incentives may vary with
the type of misconduct. Most articles retracted for fraud have
originated in countries with longstanding research traditions
(e.g., United States, Germany, Japan) and are particularly prob-
lematic for high-impact journals. In contrast, plagiarism and
duplicate publication often arise from countries that lack a
longstanding research tradition, and such infractions often are
associated with lower-impact journals (Fig. 3 and Table 1). A
highly signiﬁcant correlation was found between the journal-
impact factor and the number of retractions for fraud or sus-
pected fraud and error (Fig. 3 Aand B); the mean impact factor
was found to be signiﬁcantly higher for articles retracted for
fraud, suspected fraud, or error, compared with those retracted
for plagiarism or duplicate publication (Fig. 3D). An association
between impact factor and retraction for fraud or error has been
noted previously (4, 6, 29, 30). This ﬁnding may reﬂect the
greater scrutiny accorded to articles in high-impact journals and
the greater uncertainty associated with cutting-edge research.
Alternatively, the disproportionately high payoffs to scientists for
publication in prestigious venues can be an incentive to perform
work with excessive haste (31) or to engage in unethical practices
(4). The modest correlation between impact factor and time-to-
retraction argues against an explanation based on increased
scrutiny alone, but the higher proportion of fraud in highly
Fraud or Suspected Fraud Error
Plagiarism or Duplicate Publication Mean IF by Cause
Fig. 3. Relation of journal-impact factor to retractions for fraud or suspected fraud, error, and plagiarism, or duplicate publication. Journal-impact factor showed
a highly signiﬁcant correlation with the number of retractions for fraud or suspected fraud (A)(n=889 a rticles in 324 journals, R
=0.08664, P<0.0001) and error (B)
(n=437 articles in 218 journals, R
=0.1142, P<0.0001), and a slight correlation with the number of retractions for plagiarism or duplicate publication (C)(n=490
articles in 357 journals, R
=0.01420, P=0.0243). The mean journal-impact factor of articles retracted because of fraud/suspected fraud or error was signiﬁcantly
different from that of papers retracted because of plagiarism or duplicate publication (D) (error bars ±SEM, P<0.0001).
www.pnas.org/cgi/doi/10.1073/pnas.1212247109 Fang et al.
prestigious journals is consistent with the suggestion that the
beneﬁts of publishing in such venues are powerful incentives for
fraud (4, 6, 32). The 20 most highly cited retracted articles (Table
3) include no articles retracted for plagiarism or duplicate pub-
lication. Recent technological advances facilitating word pro-
cessing and access to electronic publications may have made
plagiarism easier to perform but have also facilitated its de-
tection (33). The impact of plagiarism and duplicate publication
on science is therefore limited; although these practices are to be
discouraged, the present study suggests that the reduction of
fraud and error should be a higher priority (32).
Our ﬁndings conﬁrm that retraction can cause a persistent
decline in citations is not inevitable (Fig. S3). The Wakeﬁeld
article in the Lancet (34) is a special case, given its sequential
partial and full retractions, extensive media attention, public
health import, and frequent citation as a source of controversy,
but it is less obvious why other retracted articles continue to be
cited. A PDF version of a 2001 Nature article by Makarova
et al. does not indicate that the article has been retracted, and
two authors disputed whether iron-containing impurities in-
validated the articles conclusions (35), which might contribute
to uncertainty as to whether the work remains valid (36). A
2005 Science article by Fukuhara et al. continues to be cited
even though both the HTML and PDF versions are clearly
marked as retracted, and the PDF version includes a copy of
the retraction notice (37). Many scientists continue to cite the
article by Fukuhara et al. for its initial identiﬁcation of visfatin
as an adipocytokine, even though the article was retracted
because of concerns about the cytokine’s reported insulin mi-
metic properties (38). This practice suggests that under certain
circumstances, scientists continue to ﬁnd utility in retracted
articles, particularly those retracted because of error, and
supports a policy of continued access to retracted articles as
long as detailed descriptions regarding the reasons for re-
traction are provided.
The longer average time-to-retraction when articles are re-
tracted because of fraud (Table 2) corroborates earlier studies
based on limited datasets (4, 39), and may be attributable in part to
the lengthy investigative process required to establish misconduct.
The trend toward a longer average time-to-retraction for articles
retracted in recent years may reﬂect a growing tendency for editors
to reach back further in time to retract articles. Recognition of
fraud can trigger a systematic review of an author’s entire research
output, resulting in a cascade of retracted articles. The correlation
Table 1. Journals with most retracted articles
Science 70 32.45
Proceedings of the National Academy
The Journal of Biological Chemistry 54 5.12
Nature 44 36.24
Anesthesia & Analgesia 40 3.07
The Journal of Immunology 34 5.86
Blood 28 9.79
The Journal of Clinical Investigation 23 15.43
Cell 22 34.77
Biochemical and Biophysical Research
The New England Journal of Medicine 16 50.08
The EMBO Journal 15 8.83
Journal of Hazardous Materials 15 4.55
Molecular and Cellular Biology 15 5.77
Infection and Immunity 14 4.06
The Journal of Biological Chemistry 37 5.12
Anesthesia & Analgesia 33 3.07
Science 32 32.45
The Journal of Immunology 30 5.86
Proceedings of the National Academy
Blood 21 9.79
Nature 19 36.24
The Journal of Clinical Investigation 17 15.43
Cancer Research 16 8.16
Cell 13 34.77
Journal of Hazardous Materials 13 4.55
British Journal of Anaesthesia 11 3.85
The EMBO Journal 11 8.83
The New England Journal of Medicine 11 50.08
International Journal of Cancer 10 4.92
Molecular and Cellular Biology 10 5.77
Science 37 32.45
Proceedings of the National Academy
Nature 25 36.24
Biochemical and Biophysical Research
Cell 7 34.77
The Journal of Biological Chemistry 7 5.12
Journal of Virology 7 5.32
The Lancet 6 33.80
Anesthesiology 5 5.19
Infection and Immunity 5 4.06
11 journals* 4* –
Molecules and Cells 8 1.99
Phytotherapy Research 7 2.47
Biotechnology Advances 5 10.96
Aesthetic Plastic Surgery 5 1.50
Annals of the New York Academy
Journal of Child and Adolescent
Archives of Iranian Medicine 4 0.97
Resuscitation 4 3.02
Clinical Rheumatology 4 1.72
The New England Journal of Medicine 4 50.08
Table 1. Cont.
International Journal of Cardiology 4 4.11
Anesthesia & Analgesia 4 3.07
Biochemical and Biophysical Research
IF, impact factor.
*Biochemistry,Blood,Contraception,The EMBO Journal,Journal of the
American Chemical Society,The Journal of Clinical Investigation,Journal
of Ethnopharmacology,The Journal of Immunology, Molecular and Cellular
Blood,Cardiovascular Research,Croatian Medical Journal,Current Eye Re-
search,European Journal of Medicinal Chemistry,FEMS Immunology &
Medical Microbiology,Journal of Cellular Physiology,Journal of Clinical On-
cology,Journal of Experimental & Clinical Cancer Research,Journal of Med-
ical Primatology,Journal of the Pakistan Medical Association,Langmuir,
Neurosurgery,Transplant Proceedings,Viral Immunology, and Yonsei Med-
Fang et al. PNAS
October 16, 2012
between time-to-retraction and impact factor (Fig. 4B)suggests
that the greater visibility and enhanced scrutiny of high-impact
journals may contribute to more rapid retraction of fraudulent
papers by these journals, although the effect appears to be
Most articles by authors with large numbers of retractions (Table
S2) were retracted because of misconduct, and these include some
of the most notorious cases in the history of research ethics. The
Mori case (Fig. S2) demonstrates that fraudulent articles can go
undetected for many years. Such cases may be revealed only for-
tuitously when exposed by an attentive reviewer or whistleblower
(40). Twelve of Mori’s retracted articles had been in the literature
for 5 y or more, demonstrating that the impact of serial retractions
on the average time-to-retraction can be substantial.
In conclusion, a comprehensive review of 2,047 articles re-
tracted from the biomedical literature reveals that misconduct has
played a more prominent role than previously appreciated. Our
ﬁndings underscore the importance of vigilance by reviewers,
editors, and readers, and investigations by institutions, govern-
ment agencies, and journalists in identifying and documenting
research misconduct. Furthermore, our ﬁndings suggest a need for
increased attention to ethics in the training of scientists. However,
this attention alone is unlikely to be successful in curbing poor
The rise in the rate of retractions raises concern about the
health of the scientiﬁc enterprise itself (32). Although articles
retracted because of fraud represent a very small percentage of
the scientiﬁc literature (Fig. 1B), it is important to recognize
that: (i) only a fraction of fraudulent articles are retracted; (ii)
there are other more common sources of unreliability in the
literature (41–44); (iii) misconduct risks damaging the credibility
of science; and (iv) fraud may be a sign of underlying counter-
productive incentives that inﬂuence scientists (45, 46). A better
Fig. 4. (A) Time-to-retraction as a function of year of retraction. R
0.1236, P=0.0414. (B) Time-to-retraction as a function of impact factor.
Journal-impact factor correlated inversely with time-to-retraction for arti-
cles retracted because of fraud (n=697, R
=0.01441, P=0.0015) but not
Table 2. Mean time-to-retraction by category
Cause of retraction n
Months to retract
All causes* 2,047 32.9 34.2
Fraud (fabrication/falsiﬁcation) 697 46.8 38.4
Suspected fraud 192 29.4 30.0
Plagiarism 200 26.0 32.6
Duplicate publication 290 27.0 30.1
Error 437 26.0 28.0
Other 108 19.8 31.1
Unknown 182 22.1 25.4
*Some articles fall into more than one category.
Table 3. Most cited retracted articles
First author Journal Year published Year retracted Times cited* Reason for retraction
Wakeﬁeld Lancet 1998 2004; 2010 758 Fraud
Reyes Blood 2001 2009 740 Error
Fukuhara Science 2005 2007 686 Error
Nakao Lancet 2003 2009 626 Fraud
Chang Science 2001 2006 512 Error
Kugler Nature Medicine 2000 2003 494 Fraud
Rubio Cancer Research 2005 2010 457 Error
Gowen Science 1998 2003 395 Fraud
Makarova Nature 2001 2006 375 Error
Hwang Science 2004 2006 368 Fraud
Potti The New England Journal of Medicine 2006 2011 361 Fraud
Brugger The New England Journal of Medicine 1995 2001 336 Fraud
Van Parijs Immunity 1999 2009 330 Fraud
Potti Nature Medicine 2006 2011 328 Fraud
Schön Science 2000 2002 297 Fraud
Chiu Nature 2005 2010 281 Error
Cooper Science 1997 2005 264 Fraud
Le Page Cell 2000 2005 262 Error
Kawasaki Nature 2004 2006 243 Fraud
Hwang Science 2005 2006 234 Error
*As of June 22, 2012.
www.pnas.org/cgi/doi/10.1073/pnas.1212247109 Fang et al.
understanding of retracted publications can inform efforts to
reduce misconduct and error in science.
Given that most scientiﬁc work is publicly funded and that
retractions because of misconduct undermine science and its
impact on society, the surge of retractions suggests a need to
reevaluate the incentives driving this phenomenon. We have
previously argued that increased retractions and ethical breaches
may result, at least in part, from the incentive system of science,
which is based on a winner-takes-all economics that confers
disproportionate rewards to winners in the form of grants, jobs,
and prizes at a time of research funding scarcity (32, 46, 47). We
have also proposed a set of reforms to strengthen the scientiﬁc
enterprise, ranging from improved training of scientists to the
identiﬁcation of mechanisms to provide more consistent funding
for science (32, 46). Solutions to address the speciﬁc problem of
retractions may include the increased use of checklists by authors
and reviewers, improved training in logic, probability and statis-
tics, an enhanced focus on ethics, the formation of a centralized
database of scientiﬁc misconduct, the establishment of uniform
guidelines for retractions and retraction notices, and the devel-
opment of novel reward systems for science (32). Dedicated
national agencies, such as the US Ofﬁce for Research Integrity,
can play an invaluable role in supporting and overseeing in-
stitutional investigations of alleged misconduct. We hope that the
present study will prompt discussion among scientists and the
society they serve to ﬁnd measures to improve the quality and
reliability of the scientiﬁc literature.
The database used for this study was compiled from a search of all articles
indexed by PubMed as retracted publications in English on May 3, 2012.
Articles were classiﬁed according to cause of retraction as fraud, suspected
fraud, error, plagiarism, duplicate publication, other, or unknown on the
basis of retraction announcements. In addition, retracted articles were cross-
checked against the annual reports of the Ofﬁce of Research Integrity. An
internet search using the Google search engine was performed to seek ad-
ditional information regarding retracted articles for which the reason for
retraction remained unclear, and included Retraction Watch, news media,
and other public records. In one case, an author was contacted to clarify
a published retraction notice. Each classiﬁcation decision was independently
reviewed by all authors and any discrepancies were resolved. Impact factors
were based on the 2011 edition of Journal Citation Reports Science Edition
(Thomson Reuters, released June 28, 2012) (48), and 5-y impact factors were
used when available. In one case (Acta Crystallographica A), the 2011 impact
factor (2.076) was used instead of the 5-y impact factor (30.646), because the
latter was felt to be anomalous. Journals without an impact factor were
assigned a value of 0.1. Statistical analyses were performed using Prism
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