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| Journal articles, contributions to books and working papers |
| PhD Thesis |
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 van Zeebroeck, N. (2008), Essays on the Empirical Analysis of Patent Systems, PhD Dissertation in Economics and Management, ULB, March 2008.
Abstract : This dissertation analyses empirically specific recent developments in the European patent system. In particular, patenting strategies adopted by applicants have substantially evolved over the past decades, contributing to the surge in workload at the patent office, raising concerns about patent quality, generating legal uncertainty, and potentially leading to real abuses of patenting procedures. |
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| Technological specialization |
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 van Zeebroeck, N., B. van Pottelsberghe de la Potterie, W. Han (2006), Issues in Measuring the Degree of Technological Specialization with Patent Data, Scientometrics, Vol. 66(3), 481-492.
Abstract : In this paper, we analyze the impact of three starting choices that must be made when measuring technological specialization with patent data: the statistical measure, the data source and the aggregation level. The statistical analysis suggests that the data source and aggregation level affect significantly the measure of technological specialization. It seems that the most reliable measure would rely on EPO data, with Gini or C20 as statistical measure, and a 4 Digit IPC classification. |
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Patent systems and patenting practices |
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 van Zeebroeck, N., B. van Pottelsberghe de la Potterie, N. Stevnsborg, D. Guellec and E. Archontopoulos (2008), Patent Inflation in Europe, World Patent Information, 30(2), 43-52.
Abstract : Patent filings worldwide have been subject to a combined growth in terms of the number of applications filed and their size. This is putting patent systems under tremendous pressure, as witnessed by the evolution of backlogs at several patent offices. The present article presents an analysis of the evolution in patent voluminosity observed at the European Patent Office (EPO) over the past two decades. The results demonstrate that the average size of applications has doubled during this period and that the largest influence comes from applications filed via the PCT route and/or with a US priority application. Voluminosity indicators are clearly influenced by geographical origins and technological areas. The increasing voluminosity has a significant impact on EPO workload and processing efficiency. There is therefore a justified need for regulatory action. Evidence from recent changes in US patent fee policy is shown to have a significant knock-off effect on voluminosity indicators for second filings at the EPO. |
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 Archontopoulos, E., D. Guellec, N. Stevnsborg, B. van Pottelsberghe de la Potterie and N. van Zeebroeck (2007), When small is beautiful: measuring the evolution and consequences of the voluminosity of patent applications at the EPO, Information Economics and Policy, 19(2), 103-132.
Abstract : The joint increase in the number and size (or voluminosity) of patent applications at the EPO raises serious concerns about the ability of patent systems to master the induced workload. This paper addresses the measurement issues of the voluminosity of patent applications and highlights some patterns in this increasing voluminosity. A new database of over 2 million documents filed at the EPO is exploited. The results show that the average voluminosity of patent applications at the EPO has doubled over the past 20 years and that it is mainly associated with applications that have taken the PCT route and which have a US priority application. Voluminosity indicators may also be influenced by the geographical origin and the technological area of the patent. The voluminosity of filings has a strong impact on the workload of the EPO, justifying the need for regulatory and policy actions. |
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 van Zeebroeck, N., B. van Pottelsberghe de la Potterie and D. Guellec (2009), Claiming more: the increased voluminosity of patent applications and its determinants, Research Policy, Vol. 38, No. 6 (July 2009).
Presented at : EPIP Conference, Copenhagen, March 2005 | SPRU (Univ. of Sussex), Brighton, June 2005 | ZEW Conference, Mannheim, September 2005 | AEA Conference, Paris, October 2005 | Centre for Advanced Studies in Law & Economics Seminar (Ghent University), Brussels, October 2006 | Steunpunt O&O Statistieken (KUL University), Leuven, November 2006 | IAMOT Conference, Miami, May 2007 | 4th CEPR Applied IO School, Tarragona, May 2007| EEA/ESEM Annual Congress, Budapest, August 2007.
Awards : IAMOT 2007 - Winner of the best student paper award, Miami, Florida (US), May 2007.
Abstract : The size of patent applications has doubled over the past two decades, resulting in a dramatic surge in patent offices' workload all over the world. This paper investigates the sources of this inflation in claims and pages for EPO applications. Four hypotheses are quantitatively tested: the diffusion of national drafting practices, the complexification of research activities, the emergence of new sectors, and patenting strategies. The results first reveal major differences across countries in patent drafting styles, especially between Civil and Common Law countries, the latter being characterized by much larger patents. Second, the success of the PCT route is leading to the harmonization of drafting styles worldwide toward the U.S. model, suggesting that the verbosity of patent drafters is not only due to the greediness of patentees but also to changes in patent systems. Finally, filing strategies, emerging sectors, and technological complexity are also important factors affecting the voluminosity of patents. |
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 van Zeebroeck, N. (2008), Développement et impact des stratégies de dépôt de brevets, Reflets & Perspectives de la Vie Economique, 2008(3), 87-100.
Abstract : This article proposes an analysis of the evolution and determinants of patent filing strategies and their impact on the patent system. Its motivation resides in the evolution of practices (patent drafting and filing) over the past 20 years, characterized by a surge in the number and size of patent applications. These developments could compromise the ability of the patent system to fulfill its economic purpose of incentive to innovate, as the inflation in number and size of applications induce considerable backlogs and delays. Based on a unique database and different econometric models, this paper first analyses the drivers of this evolution, notably the international diffusion of practices, the growing complexity of inventions, emerging technological sectors, and the building of large patent portfolios. The association of these developing strategies with patent value is then investigated based on traditional indicators and a new composite index of patent value. Finally, a more thorough analysis of the patent length confirms that these strategies are strongly associated with patent value, but mostly reveal that their main effect is to slow down the examination process, resulting into legal uncertainty in the patent system and raising several policy implications. |
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| Patent value |
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 Guellec, D., B. van Pottelsberghe de la Potterie and N. van Zeebroeck (2007), Patent as a market instrument, in Guellec D. and B. van Pottelsberghe de la Potterie, The Economics of the European Patent System, Oxford University Press, Chapter 4, 85-113.
Abstract : This chapter investigates the use and impact of patents on markets. Patent strategies are variegated and often sophisticated, far beyond the basic justification of patent systems. Strategic patenting (patent thickets, picket fences, inventing around, defensive patenting) behaviours inevitably translate into a snowball effect of patent applications by the business sector. Licensing-out and licensing-in are also more frequent practices, as witnessed by the growth of the market for technology. The increased number of patents, their highly skewed value distribution, and their more sophisticated exploitation has strengthened the need for reliable valuation methods, including the cost, market, and income approaches. IP rights are gradually being used as financial instruments, including as collaterals to loans, securitized assets, and tradable assets. |
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 van Pottelsberghe de la Potterie, B. and N. van Zeebroeck (2008), A Brief History of Space and Time: the Scope-Year Index as a Patent Value Indicator Based on Families and Renewals, Scientometrics, 75(2), 319-338.
Presented at : AEA Conference, Strasbourg, June 2007 Abstract : The renewal of patents and their geographical scope for protection constitute two essential dimensions in a patent’s life, and probably the most frequently used patent value indicators. The intertwining of these dimensions (the geographical scope of protection may vary over time) makes their analysis complex, as any measure along one dimension requires an arbitrary choice on the second. This paper proposes a new indicator of patent value, the Scope-Year index, combining the two dimensions. The index is computed for patents filed at the EPO from 1980 to 1996 and validated in its member states. It shows that the average value of patent filings has increased in the early eighties but has constantly decreased from the mid-eighties until the mid nineties, despite the institutional expansion of the EPO. This result sheds a new and worrying light on the worldwide boom in patent filings. |
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 van Zeebroeck, N. (2010), The puzzle of patent value indicators, Economics of Innovation and New Technology, In press.
Presented at : EPIP Conference, Munich, September 2006 | Steunpunt O&O Statistieken (KUL University), Leuven, November 2006 | PATSTAT Conference, Venice, October 2007 | 12th International Schumpeter Society Conference, Rio de Janeiro, July 2008. Abstract : Given the growing size of patent databases and portfolios, scholars and practitioners alike need metrics to help them in weighting patent counts or in ranking patents to focus on the most important ones. The main objective of this paper is to help them in this task with a practical and replicable approach. The discriminating criterion chosen is the potential market for the patented invention and the approach uses five different patent features (forward citations, grant decisions, families, renewals, and oppositions) that (1) have been found positively correlated with the value of patents in the literature, (2) can be extracted from patent databases, and (3) could inform on the existence of a potential market for the invention. The paper therefore discusses the main methodological issues in measuring and interpreting these metrics over a large international dataset and proposes one approach to extract from the different measures a consistent score that can be used to weight or rank patents. |
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van Zeebroeck, N. and B. van Pottelsberghe de la Potterie (2008), The vulnerability of patent value determinants, Economics of Innovation and New Technology, In press.
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 van Zeebroeck, N. and B. van Pottelsberghe de la Potterie (2008), Filing strategies and patent value, Economics of Innovation and New Technology, In press.
Presented at : IAMOT Conference, Miami, May 2007 | EPIP Conference, Lund, September 2007 | EPO Economic Advisory Group, Munich, November 2007 | 3rd ZEW Conference on the economics of innovation, Mannheim, June 2008 | EcoMod Conference 2008, Berlin, July 2008 | Annual Meeting of the Academy of Management, Anaheim, CA, August 2008. Abstract : This paper aims at contributing to the literature on the determinants of patent value. First, it puts forward a new class of value determinants in the form of filing strategies (encompassing filing routes and drafting styles). Second, it provides empirical evidence suggesting that these strategies are consistently and positively associated with patent value indicators. The empirical implementation relies on a uniquely large dataset, which allows running large-scale sensitivity tests. The results reveal that the new determinants this paper puts forward are the most stable of all. They also underline strong dependencies of several 'classical' results to the dependent variables and sampling methodologies, partly explaining several inconsistencies observed in the literature.. |
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 van Zeebroeck, N. (2007), Patents only live twice: a patent survival analysis in Europe, CEB Working Paper 07-028.
Presented at : 3rd EPIP Conference, Bern, October 2008 | FEB Seminar at KUL, Leuven, October 2008 | 5th ICIM Conference, Maastricht, December 2008 | 2008 AEA Conference, Tokyo, December 2008. Abstract : The length of patent rights is an issue of considerable importance in the design of patent systems, and its optimality has been intensively discussed in the literature. This dimension - taking the form of the number of years during which a given patent has been maintained - has been considered in the empirical literature as a direct indication of the private value of patents. But the lack of comprehensive data on both the renewal of patents and their characteristics has prevented so far any systematic analysis of the determinants of this duration. Relying on a comprehensive dataset including detailed information on all patent applications filed to the European Patent Office from 1980 to 2000 and on the renewal of those of them that were granted, this paper presents a survival time analysis of the determinants of patent length in Europe. The results are threefold: first, they clearly establish that patent rights have significantly increased in length over the past decades despite a small decline in the average grant rate, and due to the dilatation of the examination process and higher maintenance rates. Second, they show that some filing strategies induce considerable delays in the examination process, possibly to the benefits of the patentee, but most certainly to the expense of legal uncertainty on the markets and undue exploitation of the provisional protection granted to pending applications by the European Patent Convention. And third, they confirm that more valuable patents (more cited or covering a larger geographical scope) take more time to be processed and live longer, whereas more complex applications are associated with longer decision lags but also with lower grant and renewal rates. These results have many policy implications for technology markets, patent systems and all their stakeholders. |
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 van Zeebroeck, N. (2008), Long live patents: the increasing life expectancy of patents and its determinants, CEB Working Paper 08-040.
Presented at : PATSTAT Conference 2008, Vienna, September 2008 | 5th ICIM Conference, Maastricht, December 2008 | 2008 AEA Conference, Tokyo, December 2008. Abstract : The length of patent rights is an issue of considerable importance in the design of patent systems, and its optimality has been intensively discussed in the literature. This dimension has been considered in the empirical literature as a direct indication of the private value of patents. But the lack of comprehensive data on both the renewal of patents and their characteristics has prevented so far any systematic analysis of the determinants of this duration. Relying on a comprehensive dataset including detailed information on all patent applications filed to the EPO from 1980 to 2000 and on the renewal of those of them that were granted, this paper presents a survival time analysis of the determinants of patent length in Europe. The results are threefold: first, they clearly establish that the life expectancy of patent rights has significantly increased over the past decades despite a small decline in the average grant rate. Second, they show that some filing strategies strongly influence the length of patents, possibly due to induced delays in the examination process. And third, they confirm that more valuable patents (more cited or covering a larger geographical scope) tend to live longer. |
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 van Zeebroeck, N. (2009), Filing strategies and the increasing duration of patent applications, CEB Working Paper 09-005.
Abstract : It has long been implicitly assumed that the roaring backlogs experienced by most patent offices around the world – and harshly criticized by many patentees – are a mere mechanical consequence of surging numbers of patent filings. However, different voices suggest that the patent system may sometimes be gamed by an applicant in order precisely to delay the time when a decision will be taken as to the patentability of his application. By empirically showing the impact of several procedural options chosen by patentees in filing their applications at the EPO, this paper clearly demonstrates that this possibility is real, and probably not anecdotal. Deliberate or not, the main consequence of several procedural options is clearly to delay the grant decision. Why and how firms could win any benefit from such strategies can only be guessed, but whether such behaviours are legitimate or not, socially desirable or not, remains an open question. |
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 van Zeebroeck, N. (2009), From patent renewals to applications survival: do portfolio management strategies play a role in patent length?, CEB Working Paper 09-028.
Abstract : The decision of firms to renew their patents is largely assumed to be the result of a careful valuation exercise to balance their expected revenues with renewal fees. This article extends this line of reasoning to all patent applications filed to the EPO over a 20 years period and analyzes with a survival time model the determinants of their maintenance throughout their life, from filing to withdrawal, refusal or lapse. The results first show that the classical patent value proxies (families, claims, IPC classes and forward citations) constitute strong predictors of the entire length of patent rights and even more so before their grant than after, suggesting that the length of an application, even non granted, is indicative of its expected private value to the firm. They suggest that the IP management strategies of the firms aiming at building large portfolios or families to protect their inventions make them less selective in their renewal decisions. Finally, the results suggest that even the length of non granted applications (i.e. the duration of their examination) is significantly influenced by factors relating to their scope and importance and to the patenting strategy of the firms and is therefore partly in control of the applicant, particularly through the PCT option and the filing of divisionals. |
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| Research use of patented inventions and academic patenting |
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 van Zeebroeck, N., B. van Pottelsberghe de la Potterie and D. Guellec (2008), Patents and Academic Research: A State of the Art, Journal of Intellectual Capital, 9(2), 246-263.
Abstract : The sharp increase in academic patenting over the past 20 years raises important issues regarding the generation and diffusion of academic knowledge. Three key questions may be raised in this respect: What is behind the surge in academic patenting? Does patenting affect the quality and quantity of universities' scientific output? Does the patent system limit the freedom to perform academic research? The present paper summarizes the existing literature on these issues. The evidence suggests that academic patenting has only limited effects on the direction, pace and quality of research. A virtuous cycle seems to characterise the patent-publication relationship. Secondly, scientific anti-commons show very little effects on academic researchers so far, limited to a few countries with weak or no research exemption regulations. In a nutshell, the evidence leads us to conclude that the benefits of academic patenting on research exceed their potential negative effects. |
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| Knowledge Management |
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van Zeebroeck, N. (2009), Measuring knowledge and intellectual capital with patents: pitfalls and challenges (forthcoming)
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van Zeebroeck, N. (2009), Knowledge Management: A state of the art and future tracks (forthcoming)
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| Data mining, text mining and link analysis |
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Mantrach, A., N. van Zeebroeck, P. Francq, M. Shimbo, H. Bersini and M. Saerens, Semi-supervised Classification and Betweenness: Centrality Computation on Large, Sparse, Graphs (forthcoming)
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| Ongoing work |
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Patenting for euros: International patenting and foreign venture capital funding, with Stuart Graham (GeorgiaTech)
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The determinants of patent oppositions at the EPO, with Bruno van Pottelsberghe (ULB) and Antoine Bruyns (ULB and Bain & Co)
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From wires to partners: how the Internet has fostered R&D collaborations among firms, with Chris Forman (GeorgiaTech)
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Knowledge management, appropriation and firm performance, with Marco Ceccagnoli (GeorgiaTech)
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Using link and graph analysis techniques to build new patent value indicators, with Amin Mantrach (ULB) and Marco Saerens (UCL)
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Using document clustering for automatic thesaurus construction, with Pascal Francq (ULB) and Marco Saerens (UCL)
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Comparing and combining text mining and link analysis to classify documents, with Hugues Bersini (ULB), Amin Mantrach (ULB) and Marco Saerens (UCL)
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Automatic identification of dense areas in a graph of patents, with Marco Saerens (UCL) and Amin Mantrach (ULB)
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Multi-criteria ranking of patents, with Pascal Francq (ULB)
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Automatic prediction of links or citations between patents, with Hugues Bersini (ULB), Amin Mantrach (ULB) and Marco Saerens (UCL)
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