University finds Dutch economist guilty of misconduct; he responds

Peter Nijkamp

The Free University of Amsterdam found Peter Nijkamp, one of the nation’s leading economists who has lost several papers for self-plagiarism, has been found guilty of “questionable research practices,” according to the newly released results of an investigation.

Nijkamp has published a strongly worded criticism of the report (at least according to Google Translate, since his writing is in Dutch).

According to independent student publication Ad Valvas, the commission, led by Jaap Zwemmer, a professor emeritus at the University of Amsterdam, found Nijkamp was guilty of “questionable research practices.” University rector Frank van der Duyn Schouten, on the other hand, said in an official statement that there was “insufficient basis” to claim questionable research practices for each article.

The scandal first broke when the school canceled the thesis defense of one of Nijkamp’s graduate students, Karima Kourtit, due to plagiarism. According to Volkskrant (in Dutch), a report published anonymously on the website for VSNU, the Association of Universities, also accused Nijkamp himself of self-plagiarism.

The Review of Economic Analysis later retracted two of Nijkamp’s papers for self-plagiarism.

Now, a report from a commission convened by the school has found him guilty of “questionable research practice” after finding 60 out of 261 articles had “frequent reuse” issues:

The frequent reuse of fifty words or more, from texts authored by himself, or jointly with co-authors, has emerged from the inquiry into Nijkamp’s publications. Most of the overlapping passages would appear to involve his own work, with or without co-authors, and to a far smaller extent to involve the work of others. This leaves the Committee with the impression that the practice of cutting and pasting served to support a possible strategy aimed more at achieving a high number of publications than an original oeuvre.

The size of the texts that were reused varies. In some cases it was just a few sentences, but in others whole paragraphs were copied. It is conspicuous that minor adjustments were frequently made by changing, deleting or adding a few words. Mostly, references to texts used previously were absent. In some cases where a reference to a publication did appear in the text, it was not made clear that the text had been literally reused.

Although the size of the overlapping passages without reference that were encountered varied, the Committee is of the opinion that the number of publications in which passages of this kind were encountered, which is 60 out of 261, or over twenty per cent, is substantial.

Of the 60 articles with overlap, 43 were peer-reviewed papers.

The Executive Board of the school sent us a summary of the report, which endorsed the report but disagreed on some finer points:

The Executive Board has not adopted the term “Questionable Research Practice”, which was used by the Zwemmer Committee. This is because the term, by its very nature, applies to individual publications. The Committee did not examine the detailed content of individual publications. Nor has the Executive Board adopted the Zwemmer Committee’s statement that overlapping passages might account for the scope of Prof. Nijkamp’s oeuvre.

The summary includes a written statement from the rector of the university, Frank van der Duijn Schouten:

When these articles were published, the guidelines now laid down in the Dutch Code of Conduct did not exist. Partly for this reason, VU University Amsterdam has decided to refrain from further investigation into the individual publications in question. However, the outcome of the Zwemmer Committee’s investigation does raise the question of whether the principle that academic work must be original has been systematically undermined. Partly based on the Zwemmer Committee’s report, we will be intensifying the discussion of this subject within VU University Amsterdam. What standard are we using, and how should the members of the academic community call one another to account with respect to this standard?

Nijkamp’s response is strongly worded, as far as we could tell via Google Translate. His main criticisms seem to be that out of the 2,400 articles he’s published since 1972, the committee only looked at the 260 currently available digitally; many of these are “lighter genre magazines” rather than peer reviewed papers. He also disagreed with the validity of the term “self-plagiarism” itself, and was upset that the committee — or, more specifically Zwemmer — investigated the work of a dead co-author, Piet Rietveld.

Nijkamp won his country’s highest science award, the Spinoza Prize, in 1996. A spokesperson for the Free University of Amsterdam emailed us to say that Nijkamp was made an emeritus professor in January 2015. His work is heavily cited; he has an i10-index of 319 since 2010.

Update 9:40 a.m. EST 3/23/15: Nijkamp sent us a statement via email:

1.      Last year various successive anonymous allegations were raised questioning my scientific integrity.

2.      The University appointed a few committees to investigate the various anonymous complaints.

3.      The findings – in various stages – as of the beginning of this year – are:

–       one of the main sources of false information dispersion, Richard Gill (University of Leiden), has been instructed by his University to offer a public apology for scientific misconduct                 (to be published on his University website).

–       a recent verdict of LOWI (a kind of national court on scientific integrity) has convincingly proclaimed that any accusation of violation of scientific integrity from my side misses any ground.               Moreover, the VU University has been found guilty by treating my case in an improper way, by drawing false conclusions and by violating confidentiality rules.

–      finally, in a recent starement the VU University has also concluded that my publication practice does not      jeopardize or violate scientific integrity rules.

So, in conclusion, my case is clean and can be closed.

The “public apology” he is referring to is a declaration by Richard Gill after an adjudication between the two professors over Gill’s publishing the initial accusations against Kourtit. You can read some background on ThePostOnline (in Dutch), and the declaration here. The relevant portion is below:

Ad 1) prof. Gill recognises that he has made public a document that partially contained confidential information. Gill was aware of this and took account of this at the time of publication. He has only made the decision to make the document public after extensive deliberation and on the basis of the fact that an important part of said document consisted of scientific criticism of published scientific articles. He never has, and never has had, the intention of harming the interests of the plaintiffs by publishing the document. His only wish was to elicit a scientific debate. He acknowledges that he could have used other means.

Ad 2) Prof. Gill has indicated that it has never been his intention to accuse prof. Nijkamp and dr. Kourtit of data fraud, or of any other violation of scientific integrity, and that he has never expressed these allegations. Prof. Gill has declared that he only wishes to conduct a substantial scientific discussion about the quality and results of the research. He is of the opinion that, on the basis of the available information, there are a number of ambiguities in the analysis and presentation of the research data that should be further investigated. Prof. Gill does not thereby support all conclusions and allegations that the aforementioned document contains, specifically those that relate to allegations concerning data fraud.

Like Retraction Watch? Consider supporting our growth. You can also follow us on Twitter, like us on Facebook, add us to your RSS reader, and sign up on our homepage for an email every time there’s a new post.

27 thoughts on “University finds Dutch economist guilty of misconduct; he responds”

  1. Does anyone have access to the full report? I can only find the version without appendixes; without the raw data it’s very hard to compare the claims of the committee with the claims made by Nijkamp …

  2. Please note that the first sentence of this posting (“The Free University of Amsterdam found Peter Nijkamp [..] guilty of “questionable research practices””) is incorrect. The Board of the Free University of Amsterdam fully agrees with the general findings of the report of the Zwemmer Committee, but they don’t agree with the Zwemmer Committee that the findings can be classified as “Questionable Research Practice”. Within The Netherlands, the Free University of Amsterdam is not considered as a ‘school’.
    Please note as well that Peter Nijkamp holds the opinion that ‘questionable research practice’ is an ‘unknown term’ within The Netherlands (only used in a short report of KNAW of April 2014).

  3. Mark, the Free University of Amsterdam has decided to publish the report of the Committee Zwemmer without appendixes in order to protect the privacy of the co-authors. Peter Nijkamp is in the possession of a full version. The Board of the Free University of Amsterdam has also made a clear statement to all co-authors that they should start with an investigation of these papers in order to decide if they need to be retracted or that it is sufficient to publish a correction.

  4. Mark Peletier
    Does anyone have access to the full report? I can only find the version without appendixes; without the raw data it’s very hard to compare the claims of the committee with the claims made by Nijkamp …

    A PDF comment attached to page 2 of “the version without appendixes” (which actually has one appendix, numbered 6.1) says “Ter publicatie. De bijlagen 6.2, 6.3 en 6.4 zijn niet bij het rapport gepubliceerd om de privacy van co-auteurs te beschermen die niet door de commissie zijn gehoord. CvB VU.” Google Translate renders that as “For publication. Annexes 6.2, 6.3 and 6.4 have not been published in the report to the privacy protection co-authors who are not by commission be heard. EB VU.” It would appear to me that anyone who does “have access to the full report” would, indeed, be violating the privacy of the co-authors, and might (therefore) be breaking Dutch and/or European law (as well as being—in my opinion—a bit of a weasel). Much as I too would like to “compare the claims of the committee with the claims made by Nijkamp”, I think I will have to resign myself to doing without.

    Now, Nijkamp could, I suppose, ask his co-authors for a release, and then publish the no-longer-private data that supports his case (or, if the release is not given, publish that fact). It will be interesting to see if he does anything of that sort.

  5. According to the article in the Dutch national newspaper “NRC” of last Thursday, Nijkamp has shown the list of papers in the appendix to the science journalists reporting on the latest developments, in order to support his claim. The NRC writes that Nijkamp’s claims that many of the papers in the list of 43 were not serious (peer reviewed etc etc) journal papers at all is completely false. All 43 appeared in regular journals.

  6. Maybe Nijkamp means that many of the 261 were not actually serious research publications. That’s possible. But that means that the percentage of tainted research publications goes up …

  7. The initial selection of papers was taken from the university’s own publication database, which is built up, of course, from the annual contributions from research staff. Zwemmer and colleagues investigated papers in the category “peer reviewed scientific research paper”. The category is provided by the author. They found a very large percentage of mis-classifications.

  8. To me as an editor, it depends on what part of the text the copied material came from, and whether the source material was a journal or conference-type article. Supposing it was a journal article, if it was in his Methods that he uses for a lot of studies, I’d ask him to rephrase it. If it came from the Introduction I’d be more upset. If it was a bunch of sentences in the Abstract, Results, or Discussion, I’d most likely reject the paper outright. If it was from a conference article on the other hand, whatever section it came from, supposing it was on the order of a paragraph or more, I’d ask him to rephrase it, to avoid violating the copyright. If it was entire pages and figures then I would reject it. Republishing of lightly reviewed conference-type studies in a journal is allowed, but they can’t be copied verbatim. And besides that, if there was too much conference paper copy, I would suppose it was conference paper quality, and feel the need reject it outright.

    1. Edward John Ciaccio
      if it was in his Methods that he uses for a lot of studies, I’d ask him to rephrase it. If it came from the Introduction I’d be more upset.

      A question for you as editor
      The ways to rephrase a method could be many but are not infinite. So to avoid that, authors just add, “as previously described” and add a citation of a previous article with the same method.
      Now sometimes that generates a nested system of citations, cause the cited paper cited for the technique another paper, sometimes on multiple levels, generating a time consuming process for the reader.
      Now, since the possibility for web supplementary, could not be convinient to have a Supplementary methods section complete of the descriptions of all the techniques without citations? that would be possible just if for this section the plagiarism will not be considered.

      In addition, the sentence “as previously described” is the most plagiarized of scientific literature.

  9. The original complaint by the anonymous whistleblower was not a complaint about plagiarism at all. The whistleblower noticed that the texts of numerous papers collected together in a PhD thesis (all 15 or so papers were joint papers by student and supervisor) were quite simply unintelligible. The text of one paragraph contradicts the previous one, without the author making any remark about this. The conclusions don’t follow from the observations or the data. It turned out that these mutually contradicting passages were copy-pasted from earlier publications. The complaint was about *quality* not about *integrity*. The committee Zwemmer thinks that the senior co-author used this strategy deliberately simply to create an enormous research output (Nijkamp is the number one economist in the world, with respect to quantity).

  10. I would like to ask Peter Nijkamp to disclose the full version of the report of the Committee Zwemmer so anyone can compare the statements and the findings of the Committee Zwemmer against the statements of Peter Nijkamp.
    It seems to me that the peer-reviewed paper “Evaluation of cyber-tools in cultural tourism” ( ) will be a part of the papers investigated by the Committee Zwemmer. An (almost?) identical version (‘Research Memorandum 2011-30’) can be downloaded for free from
    I have a PDF of the version which was published in the IJSD and it seems to me that this version is (nearly) identical to the version which can be downloaded for free.
    The anonymous complainer has the opinion that the scientific level of a huge amount of the more recently published peer-reviewed papers of Peter Nijkamp is (extremely) low (or just plain rubbish). I have read the paper ‘Evaluation of cyber-tools in cultural tourism’. I fully agree with his conclusion. There is no need to have a degree in economy to be able to read and to understand this paper.
    Anyone over here who has an opinion about the level of this paper? Anyone any idea about the scientific level of the journal IJSD (and / or about the publisher )?
    Please note as well that Richard Gill has started a crowdfunding project ( ) in order to get a proper translation of the full report of the anonymous whistleblower.

  11. Klaas van Dijk
    I would like to ask Peter Nijkamp to disclose the full version of the report of the Committee Zwemmer so anyone can compare the statements and the findings of the Committee Zwemmer against the statements of Peter Nijkamp.

    I don’t think Nijkamp is in a position to do so.
    You will have to ask the VU.

    1. The newspaper NRC obtained the appendix of the Drenth report from the VU. Two NRC science journalists checked Nijkamp’s claims that many of the articles were *not* peer-reviewed research papers in regular journals, but instead included all kinds of secondary material. Their conclusion was that Nijkamp’s objections were completely without any ground.

  12. Peter Nijkamp “was upset that the committee — or, more specifically Zwemmer — investigated the work of a dead co-author, Piet Rietveld.”
    I tend to think that all these peer-reviewed papers with Piet Rietveld as a co-author will have VU as affiliation. This implies that VU is also responsible for the contents of all of these papers and this also implies that VU is free to scrutinize any of these papers (conducted by the Committee Zwemmer, or conducted by another Committee convened by VU). I fail to understand the point of view of Peter Nijkamp.

    1. I would like to know under what conditions it would be forbidden to investigate a scientific work. I had the understanding that this should always be possible. So are there any laws or other kind of rules that limit such investigations, and have these clearly been communicated to the scientific community?

      I also fail to see what kind of information in the appendices of the Zwemmer report cannot be disclosed, in order to protect the privacy of co-authors who had not been heard by the commission.

    2. I guess his concerns are that Rietveld can no longer defend himself. As they say in the Netherlands, “over de doden niets dan goeds”.

  13. Dear Retraction Watch

    Peter Nijkamp has apparently stated the following in an email to you: “one of the main sources of false information dispersion, Richard Gill (University of Leiden), has been instructed by his University to offer a public apology for scientific misconduct (to be published on his University website)”.

    This is not accurate.

    Peter Nijkamp and Karima Kourtit certainly put in a complaint to my university. Unfortunately, according to the Leiden University regulations, I am not at liberty to publish it. I would be delighted if Nijkamp and Kourtit did do that.

    Their complaint was handled by the committee for scientific integrity of Leiden University. After hearing both parties, first separately and then together, the committee decided to try to settle the complaint “out of court”. After some negotiations, a wording of a declaration by me was agreed by the two parties and I published it on my website as agreed.

    Please note that I was not obliged to do this by the board of my university. As I said, the case was settled “out of court”. I made the declaration completely of my own free will, and I stand 100% behind it. The board of Leiden University was informed of the outcome, that’s all. According to our agreement, the case is now closed, without any further proceedings against me, or for that matter, without the committee for scientific integrity actually ruling on the substance of the complaint! (which is perhaps a pity …)

    The material I had helped circulate included some material earlier submitted by the whistleblower to the ombudsman of the Free University. That small portion (three appendices to a much larger report) could possibly be considered “confidential”. I only later learned that according to the rules of scientific integrity investigations at the Free University, the complainant and complainee are not bound by confidentiality; confidentiality is only demanded of the officials who handle a complaint and scientists who advice them. The complainant was free to publish his complaint, and therefore I was presumably free to help him do just that.

    At present I am preparing a translation into English of the whistleblower’s report, and intend to publish it as soon as possible. I do not believe that the factual information in the report is “false”; on the contrary, it seems to be very reliable (which is why I helped distribute it in the first place). The many findings of the whistleblower have been confirmed by investigation after investigation, and a fourth investigation into data anomalies is underway. The only issue I would have with the whistleblower is that I personally would not like to draw the conclusion “data-fraud” prematurely, i.e., before further investigation of the data and data-analysis scripts. Which, by the way, were requested by myself a year ago. They have still not been supplied.

    We understand that an investigation is currently underway at the Free University into these anomalies, I am not involved in any way, but on the contrary am very happy that someone else is now doing this difficult job.

    In my opinion, from the start, the whistleblower’s main complaints concerned quality not integrity. Indeed, official investigations have concluded “irresponsible carelessness” with respect to some papers, as well as “questionable research practices”. However, Karima Kourtit has her PhD degree, and Peter Nijkamp is retired; the Free University understandably seems eager to let the whole affair blow over now, and does not adopt the hardest conclusions of the various enquiries at university and at national level, presumably to avoid legal ramifications which would benefit no one.

    Richard Gill

  14. A blog post of last 17 February by Dutch science journalist Frank van Kolfschooten, translated by Google&me:

    Much Ado About Nothing

    Economists Peter Nijkamp and Karima Kourtit of the Free University have filed a complaint at the Scientific Integrity Committee of Leiden University against statistics professor Richard Gill. This is evident from this ( declaration on Gill’s website.

    Gill explains on his website out what was going on:

    “June 2014 I publicized an anonymous report prepared by a whistleblower at the Free University, Amsterdam. The report criticised the content of the PhD thesis or Karima Kourtit (supervisor: prof. Peter Nijkamp) as well as half a dozen papers published by Kourtit and Nijkamp, ​​and another half a dozen by Baycan and Nijkamp. This action led to a complaint by Dr. Kourtit and Prof Nijkamp to Leiden University-which was handled by Leiden’s “Committee on Scientific Integrity” (CWI). After several at hearings-including one where clause all parties were present together, a “verklaring” (declaration) was drawn up, all parties-which Could agree to, and whereby the conflict between Kourtit and Nijkamp on the one hand, and myself on the other hand, Considered by all parties is to be settled. I am very grateful to the CWI for Their patient and careful work.

    The “verklaring” was subsequently approved by the Board of Leiden University, and is hereby (February 17, 2015) made ​​available on this website.”

    In Amsterdam we call this Much Ado About Nothing.

    A more interesting question is why the raw data that Gill had requested from Nijkamp and Kourtit have still not been made available, while the disclosure thereof had already been announced in June 2014 by Kourtit’s supervisor Henk Scholten.

    And where is the verdict of the Integrity Committee of the Free University, which has from June 2014 on examined the fraud allegations in the aforementioned anonymous report? And where are the reports of the commission Drenth 2 (alleged plagiarism in Kourtit’s first thesis) and of the commission Zwemmer (citations in Nijkamp’s complete works)?

    1. Yes, at the time I thought that the agreement between Nijkamp and me (brokered by the committee of scientific integrity) had also been approved by the board of my university, but I was later told that they had merely been informed of it.

  15. Please note that the Zwemmer Committee has investigated 261 peer-reviewed papers (co-) authored by Peter Nijkamp of which 60 (23%) were identified as containing passages with overlapping texts without a proper reference (table on page 7).
    Please note that these 60 papers can be divided in 17 papers with overlapping texts from other sources and 43 papers with overlapping texts “from the internal list of peer reviewed publications” (co-)authored by Peter Nijkamp (page 10 of the report).
    Peter Nijkamp holds the opinion that the Zwemmer Committee was only allowed to investigate peer-reviewed papers in journals which were indexed “artikelen die onderworpen zijn geweest aan een peer review proces en gepubliceerd zijn in een geïndexeerd tijdschrift (met een Web of Science, ISI of Thomson Reuters kwalificatie).”.
    The report of the Zwemmer Committee (page 5) states: “The inquiry investigated only those publications that were published in peer-reviewed academic journals. This accordingly excludes from the inquiry’s selection research memoranda, working papers, conference proceedings and publications in non peer-reviewed professional journals.”
    Peter Nijkamp (last part of his defence) holds the opinion that the Board of the Free University was not allowed to publish the report of the Committee Zwemmer. Peter Nijkamp also holds the opinion that the Board of the Free University was not allowed to let the Commitee Zwemmer finish their investigation after LOWI had advised that one of of the three allegations of plagiarism was not founded. Please note that the board of Free University still needs to make a final decision if they accept the advice of LOWI (that’s how it works in The Netherlands).
    Please note as well that Eveline van Leeuwen and Frank Bruinsma (two of the four authors of the “Cyber-Tools” paper ( have told LOWI that they don’t want to make an appeal at LOWI against the decision of the Board of the Free University that the “Cyber-Tools” paper contained alot of plagiarized parts (as concluded by the
    Committee Drenth2 and adopted by the Board of the Free University) and that this paper should be retracted. Source: the LOWI-report of this case.

  16. Ad Valvas, the independent university newspaper of the Free University, has posted a comment (in Dutch) of Professor Erik Verhoef, the Head of the Department of Spatial Economics at the Free University in Amsterdam, in which he reacts on various recent statements of Peter Nijkamp.
    Erik Verhoef disagrees with the opinion of Peter Nijkamp that it is allowed to copy/paste his own texts in order to disseminate knowledge.
    Erik Verhoef states that all kind of new knowledge (eg, preliminary findings, manuscripts, etc.) can be published online as ‘Discussion Paper’ on (all of them are free to download for the whole world, same like, eg, Manuscripts published as ‘discussion paper’ might well be published lateron in a high-ranked journal, but that will often take a lot of time.
    Erik Verhoef also disagrees with the opinion of Peter Nijkamp that it is allowed to use copy/paste for a certain group of papers which will be submitted to so-called ‘low quality’peer-reviewed journals. Peter Nijkamp himself states that peer-review for such journals only means changing tiny items and conducted by a non-academic employee (or nothing at all). Examples recorded by myself are changing Internet into internet and changing tiny details in the list with references.
    Finally, Erik Verhoef states that economists like Peter Nijkamp should stop with submitting papers to these so-called ‘low quality’ peer-reviewed journals.

  17. I was alerted to the above posting by Mr. Klaas van Dijk, which gives too crude an attempt to summarize and translate my earlier note. That note was written in reaction to statements made by Peter Nijkamp in Dutch newspaper interviews (Volkskrant; Ad Valvas), suggesting that it would be unproblematic to literally reuse one’s own texts between journal articles, without providing appropriate referencing, for the sake of knowledge dissemination. In my reaction I repeat the Dutch KNAW’s (Royal Netherlands Academy of Sciences) viewpoint that reuse of own texts at limited scale is often considered unproblematic and does not entail scientific misconduct nor questionable research practice as long as it involves introductory phrases, or phrases explaining standard theory or methods that are for example included for the sake of keeping an article self-contained. At most, such reuse of own texts can be considered inelegant, where a complication is that it is in fact inelegant to turn a reused fragment into a citation (with quotation marks and a reference) when it is really too short or too unimportant to justify a citation, but at the same time it is inelegant not to give proper referencing when the fragment becomes too substantial.
    Peter Nijkamp’s statements go an important step further, as “knowledge dissemination” to me nearly by definition implies it involves texts that readers would consider to be the original research contribution of the article. What he apparently has in mind is a model with low-quality journals for quick knowledge dissemination, after which the same knowledge can be published in higher ranked journals with longer review procedures. I would not support making such a binary distinction between low- and high-quality journals, between which new research results can be reused without referencing – and not only because it seems unworkable because journals rank on a continuous scale in practice. Nowadays, we have free online discussion papers for fast dissemination, so there is also no need to use lowly ranked journals for that purpose.
    And I would in general advice against publishing in journals that call themselves peer reviewed scientific journals when you know or suspect, in Peter Nijkamp’s own words, that the only reviewing is done by a secretary making a few remarks.

  18. The translation project (translation of the whistleblower’s 80 page document “Irregularities in publications of Nijkamp/Kourtit and Nijkamp/Baycan” is now underway: see

    Dutch speaking readers are invited to send me corrections or suggestions for improvements. If you would like to contribute to the cost, see

  19. The English translation of the whistleblower’s report is now complete, see
    It includes a new preface by the anonymous whistleblower, who has also checked the text.

    Some typographic corrections remain to be done (layout of tables, …).

    In the meantime Ms Kourtit has been awarded a second PhD degree, now at Adam Mickiewicz University, Poznan. Her new thesis “The New Urban World” can be downloaded at

Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.