`
`
`
`Improving Citation-Based Patent Value Measures
`
`Dirk Czarnitzki 1,2,3, Katrin Hussinger 4,1,3 and Bart Leten 5,1
`1 K.U. Leuven, Dept. of Managerial Economics, Strategy and Innovation (Belgium)
`2 Centre for R&D Monitoring (ECOOM) at K.U. Leuven (Belgium)
`3 Centre for European Economic Research (ZEW), Mannheim (Germany)
`4 Maastricht University, Dept. of Organization and Strategy (The Netherlands)
`5 Vlerick Leuven Gent Management School (Belgium)
`(k.hussinger@maastrichtuniversity.nl)
`
`
`
`in
`EPO, patent examiners classify patent citations
`different categories according to their relevance for the
`patent application in question (Harhoff et al., 2005; Webb
`et al., 2005; Criscuolo and Verspagen, 2008). Patent
`references that challenge the novelty or inventive step of
`the patent under examination (“blocking citations”) can be
`distinguished from references that define the state of the
`art in a technology field but are not prejudicing novelty or
`the inventive step.1
`We suggest that some types of citations are more
`highly correlated with the patent value than others. For
`instance, blocking patent citations are likely to be more
`highly correlated with the economic value of cited patents
`than other types of citations. Blocking citations indicate
`that the cited patent threatens the granting of other patent
`applications (Michel and Bettels, 2001; Harhoff et al.,
`2005), which may provide the owner of the cited patent
`with an important competitive advantage as the cited
`patent may keep competitors off markets or technologies
`that are important to the owner of the cited patent by
`legally depriving competitors from obtaining own patents
`on related inventions (Guellec et al., 2008). On the other
`hand, there are patents receiving many citations as non-
`infringing state of the art. Such patents trigger future
`patent applications and have been shown to be of higher
`technological
`importance
`that document cited as
`infringing prior art (Guellec et al., 2008). We expect that
`these patents would also generate a higher value for their
`owners but for a different reason.
`The assertion that different types of citations
`correlate more or less highly with the economic value of
`patents than other citations can be tested by adding
`measures for different citation types to the market value
`equation that is used by Hall et al. (2005) and checking
`whether this variable allows for a better assessment of the
`value of patents. The remainder of the paper suggests a
`testing strategy. The next section contains an overview of
`the literature on the valuation of firms’ knowledge assets
`and patents. Section 3 describes the patent application
`procedure at the European Patent Office (EPO). Section 4
`outlines the market value framework and section 5
`concludes.
`
`1 Another type of patent citation heterogeneity stems from the source of
`citations, i.e. examiner versus applicant given citations (Alcacer and
`Gittelman, 2006; Hedge and Sampat, 2009).
`
`Patent-based measures are the most frequently
`used indicators in empirical research on innovation and
`technological change. The first studies employing patent
`data used patent counts as indicators of innovation output
`(Scherer, 1965; Schmookler, 1966; Griliches, 1984).
`Patented inventions differ however widely in their
`technological and economic ‘value’ or ‘importance’
`(Schankerman and Pakes, 1986; Albert et al., 1991;
`Harhoff et al., 1999). In response, patent forward citations
`have been put forward as a measure for the technological
`and economic value of patents (Trajtenberg, 1990; Hall et
`al., 2005). While forward patent citations are found to
`correlate positively and significantly with patents’
`economic value reported in surveys (Harhoff et al., 1999;
`Gambardella et al., 2008) as well as with firms’ market
`value (Hall et al., 2005), forward citations appear to
`explain only very little of the actual variance in patent
`value. Studies by Gambardella et al. (2008) and Bessen
`(2008) show that forward citations explain no more than
`five percent of the actual variation in the value of
`European and US patents.
`A possible reason why forward citations explain
`little of the variance in patent value may be that citations
`to prior art are made for different reasons. The aim of this
`study is to exploit heterogeneity in patent citation types
`by analyzing whether certain types of citations correlate
`more strongly with patent value than others. It is argued
`that different citation types reflect value differences. This
`means that patent citation-based value indicators could be
`improved by taking into account different citation types.
`Information on citation types is available for patents that
`are examined at the European Patent Office (EPO). At the
`
`Abstract - A growing literature aims at determining the
`private value of patents. It has been shown that patents and
`the citations they receive by future patent applications
`contribute significantly to the private value of firms beyond
`their R&D stocks. But it has also been shown that citations
`can explain very little of the variance of the patent value
`distribution. This paper suggests that citation-based patent
`value measures can be improved by taking the reason for
`which patents are cited into account. Such information is
`available at the European Patent Office.
`
`Keywords - Patents, Citations, Patent Value
`
`I. INTRODUCTION
`
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`II.PATENT VALUE STUDIES
`
`A broad set of studies has examined the value of
`firms’ knowledge assets and patents, employing different
`methodologies. One strand of the literature focuses on the
`estimation of production functions to study the returns to
`R&D at the firm and sector level (for reviews of this
`literature see Griliches, 1995, and Mairesse and Mohnen,
`1996). Returns to innovation, however, rarely occur
`during the period in which the investment in innovation
`occurs, and in fact, may be spread over the number of
`years following such an investment. This renders current
`profits or productivity effects partial and incomplete
`indicators of the returns to innovation (see the surveys by
`Hall, 2000, and Czarnitzki et al., 2006). For this reason,
`other scholars employed the so-called market value
`approach, which is based on a seminal contribution by
`Griliches (1981), to estimate returns to innovation. The
`market value framework employs the stock market value
`as an indicator of the sum of expected future profits of the
`firm which is then related to its book value and, in
`addition, to several measures of firms’ R&D activities.
`Typically scholars have measured the knowledge stock of
`firms by the (depreciated) sum of prior R&D investments
`and/or their patent stock (e.g. Bloom and van Reenen,
`2002).
`Although the market value method is intrinsically
`
`
`limited in scope, because it can be used only for public
`firms that are traded on a well-functioning financial
`market, using this method avoids timing problems of
`R&D costs and revenues, and is capable of forward-
`looking evaluation, something that studies analyzing
`profitability or productivity during a given period of time
`are not able to do.2 Furthermore, the market value method
`is useful for calibrating various innovation measures, in
`the sense that one can measure their economic impact and
`possibly enabling one to validate these measures for use
`elsewhere as proxies for innovation value. The latter
`argument motivates our study.
`
`
`As stated above, most scholars used the R&D
`stock as measure for knowledge capital and supplemented
`it with patent stocks that may generate a premium as
`patent-protected knowledge grants the owner a temporary
`monopoly and eases appropriation of the returns obtained
`from the initial R&D investment. While R&D stocks
`reflect firms’ inputs, or investments, in R&D, patent
`stocks measure the output, or “success”, of the R&D
`investments. The typical finding of prior market value
`studies is that both R&D and patent stock variables
`correlate positively with firms’ market value, and that
`patent stocks add information on the value of firms’
`knowledge assets above and beyond R&D stocks (Hall,
`2000, Czarnitzki et al., 2006).
`
` While patent-based measures have the advantage
`that they are easily available from patent offices, cover
`
`
`2 See Czarnitzki and Kraft (2004) for an alternative method of forward
`looking evaluation. They suggested relating measures of innovation to
`firms’ credit ratings, which are also forward-looking.
`
` 590
`
`long time series and a broad range of technologies (with
`software as partial exception in some patent systems, Hall
`et al., 2007), their usefulness as output indicator of R&D
`activities is seriously affected by the fact that patented
`inventions differ widely
`in
`their
`technological and
`economic value or “importance”. The value distribution
`of patents is highly skewed. A few patents are very
`valuable, but many are worth almost nothing (Pakes,
`1985; Schankerman and Pakes, 1986; Harhoff et al., 1999;
`Deng, 2007). Thus, the estimation of an average effect of
`patent stocks may be misleading in valuing the knowledge
`assets of a firm. Hall et al. (2005) therefore suggest using
`forward patent citations as a patent value indicator in the
`market value equation. Forward citations are references to
`patents made by future patent applications. The more
`citations a firm’s patents receive, the more influential its
`patents are for future technology development, and the
`higher is the assumed economic value of a firm’s patent
`stock. While forward patent citations are found to
`correlate positively and significantly with patents’
`economic value reported in surveys (Harhoff et al., 1999;
`Jaffe et al., 2000; Gambardella et al., 2008) as well as
`with firms’ market value (Hall et al., 2005), 3 forward
`citations appear to explain only very little of the actual
`variance in patent value. Gambardella et al. (2008) show,
`based on patent value information from an inventor
`survey4, that forward citations only explain 1.4% of the
`variation in the economic value of European patents as
`reported by their inventors. Using patent renewal data to
`estimate the value of a set of patents filed at the United
`States Patent and Trademark Office (USPTO), Bessen
`(2008) similarly finds that patent citations explain only a
`very small portion (less than 6%) of the variance in patent
`value. We propose that the fact that patents are cited for
`different reasons can be taken into account in order to
`improve patent value estimates.
`
`III. DIFFERENT PATENT CITATION TYPES AT THE
`EUROPEAN PATENT OFFICE
`
`
`(EPO) was
`The European Patent Office
`
`
`established in 1977 after the ratification of the European
`Patent Convention (EPC). It’s task is to grant legal
`protection for invention on behalf of all contracting states.
`Legal protection can be granted for inventions that fulfill
`three criteria: 1) novelty, 2) inventive step and 3)
`industrial applicability according to article 52(1) of the
`EPC. Novelty is defined as not being state of the art. The
`state of the art is defined as “everything made available to
`the public by means of written or oral description, by use,
`or in any other way, before the date of filing at the
`European patent application” (EPC, articles 54(2)). The
`inventive step requires that an invention is not obvious to
`a person skilled in the art (EPC, article 56).
`
`3 There is also evidence that forward patent citations correlate positively
`with patents’ social value (Trajtenberg, 1990).
`4 See Giuri et al. (2007) for a description of the PATVAL inventor
`survey and some first descriptive results.
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`Once a patent application is filed at the EPO, the
`search divisions carry out a patentability search. The aim
`of this search is to judge the appropriateness of the scope
`of the legal protection as requested by the patent
`application. The patent grant decision is based on the
`outcome of this search for prior art. Note that other than at
`the United States Patent and Trade Mark Office (USPTO)
`the patent applicant at the EPO is not subject to the “duty
`of candor” and does not have to report relevant prior art in
`the patent application. In consequence, about 90% of all
`patent citations in EPO patents are added by the patent
`examiner (Criscuolo and Verspagen, 2008).
`The search for prior art taken out by the patent
`examiner follows The Guidelines for Examination in the
`European Patent Office5, which define a certain quality
`standard for patent examination and ensure equal
`treatment of all EPO patent applications. The examination
`guidelines explicitly require examiners to be objective and
`selective when defining the documents referred to as prior
`art. For most of the cases one to two documents are
`sufficient to determine the scope of the patent application
`in question (Michel and Bettels, 2001). This parsimonious
`and objective approach ensures that the references are a
`relevant subsample of the actual state of the art rather than
`an overview on the subject-matter of the invention
`(Harhoff and Reitzig, 2004, Harhoff et al., 2005). The
`result of the patent examiners’ search for prior art is
`summarized in the so-called patent search report.
`The Guidelines for Examination in the European
`Patent Office require that the references to prior art are
`classified according to their relevance for the patent
`application in question. Prior art can be cited as
`documents defining the non-infringing state of the art in a
`technology field (A-type references). Citations can also be
`made to restrict the patentability of the patent application,
`namely citation types X, Y and E. X-type citations are
`documents showing essential features of the invention
`under investigation or at least questioning the inventive
`step of these features if taken alone. Y-type citations
`question the inventive steps claimed in the invention
`being examined, when combined with one or more
`documents
`(Harhoff et al., 2005; Criscuolo and
`Verspagen, 2008). 6 E-type citations are conflicting
`documents that are published on or after the filing date of
`the patent application in question. We label X, Y and E-
`type citations as blocking citations in line with prior
`research (e.g. Guellec et al., 2008). Prior research has
`shown that patents which receive backward blocking
`citations have a lower probability to get granted (Guellec
`
`
`5 See http://www.epo.org/patents/law/legal-texts/guidelines.html.
`6 The Guidelines for Examination in the European Patent Office present
`two examples for references to be marked with a “Y” (see Chapter X,
`paragraph 9.1.2). First, the combination of patents and scientific
`documents which typically cover rather basic technological advances
`that need to be combined with applied technologies to be novelty
`challenging (Della Malva and Hussinger, 2010) are Y-type citations.
`Second, patent families that threaten the novelty of patent applications
`are cited as Ys.
`
` 591
`
`et al., 2008) and a higher probability to face opposition
`after granting since they are “weak” patents (Harhoff and
`Reitzig, 2004; Czarnitzki et al., 2009). Note that a patent
`application can still be granted if it receives backward
`blocking citations (although this is less likely). This can,
`for instance, be the case for patent applications with many
`claims. Blocking citations may only pertain to single
`claims and the remaining claims can be strong enough to
`get a modified patent application granted. Table I shows
`the full citations classification of the EPO.
`In this paper, we argue that different citations
`types can be used to get a better understanding of the
`patent value. While A-type citations are likely to suggest
`patents of high technological relevance that trigger future
`patents without restricting their novelty, X, Y, E-cites
`might have a high importance in technology markets as
`they can block related patent applications.
`
`
`T
`
`TABLE I
`DIFFERENT CITATION TYPES AT THE EPO
`
`X particularly relevant documents when taken alone
`(implies: the claimed invention cannot be considered
`novel or cannot be considered to involve an inventive
`step)
`Y particularly relevant if combined with another
`document of the same category
`A documents defining the general state of the art
`O documents referring to non-written disclosure
`intermediate documents (documents published
`P
`between the date of filing and the priority date)
`documents relating to theory or principle underlying
`the invention (documents which were published after
`the filing date and are not in conflict with the
`application, but were cited for a better understanding
`of the invention)
`E potentially conflicting patent documents, published
`on or after the filing date of the underlying invention
`D document already cited in the application
`Source: Webb et al.(2005)
`
`
`
`III. SUGGESTESD METHODOLOGY
`
`
`
`Following Griliches (1981) a market value
`
`approach can be applied to assess the private value of
`firms’ knowledge assets, including patents that receive
`different types of citations. The market value approach
`draws on the hedonic price model in viewing firms as
`bundles of assets and capabilities, from plants and
`equipment to intangible assets such as brand names, good
`will and knowledge. It is difficult to disentangle firms’
`assets
`and
`capabilities
`since
`they
`are
`priced
`simultaneously on the market. The market value approach
`assumes that financial markets assign a valuation to the
`firm’s assets bundle that is equal to the present discounted
`value of their future cash flows. A number of recent
`empirical studies used the market value approach to
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`
`
`(
`as:
`
`
`
`
`
`
`
`
`
`
`
`
`
` (1)
`
`estimate the economic value of knowledge assets of firms
`(Hall et al., 2000; Czarnitzki et al., 2006).
`
`
`Following most existing studies the following
`market value equation can be assumed, relying on the
`assumption that a firm’s assets enter additively. This leads
`to the following equation, with A representing the
`physical assets and K the knowledge assets of firm i at
`time t:
`
`
`Under the assumption of constant returns to scale
`) equation (1) can be rewritten in logarithmic form
`
` (2)
`
`
`The left hand side of the equation is the log of
`Tobin’s Q, defined as the ratio of the market value to the
`replacement cost of the firm’s physical assets. The
`marginal or shadow value of the ratio of knowledge
`capital to physical assets is represented by γ. It captures
`the expectations of the investors over the effect of the
`knowledge capital relative to physical assets on the
`discounted future profits of the firm. Log q is the intercept
`of the model.
`
`Prior studies used different variables to capture
`the knowledge assets K of a firm. First, the stock of firm’s
`R&D expenses is often used as a measure for firms’
`investment into R&D. As R&D activities are highly
`uncertain activities, the stock of patent applications is
`typically used as a measure for successfully finished R&D
`activities. Since previous literature has shown that the
`distribution of patent value is highly skew (Pakes, 1985;
`Schankerman and Pakes, 1986; Harhoff et al., 1999;
`Deng, 2007; Gambardella et al., 2008) the stock of
`forward citations, i.e. citations patents receive by later
`filed patent applications, has been introduced into the
`market value literature as a measure for the importance of
`patents (Hall et al., 2005).
`We suggest that within this framework different
`forward citation types that patent receives at the EPO can
`be distinguished. For instance, the stock of blocking
`patent citations can be used to test whether blocking
`citations (X, Y and E-type citations) correlate more
`strongly with market value than other types of patent
`citations. Similarly, the stock of non-infringing building
`patents can be added to the market value equation in order
`to test whether these patent with a potentially superior
`technological content have a higher impact on the market
`value than other patent citations. This results in the
`following empirical specification:
`
`
`
`
` (3)
`
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`The coefficients in this cascading specification
`
`
`have to be interpreted as a premium or a discount on the
`former variable (Hall et al., 2005). For example, if the
`R&D stock over assets has a positive impact, a positive
`estimated coefficient of the patent stock over the R&D
`stock would reflect a premium of successfully finished
`R&D projects (as visible in patents) on top of the positive
`evaluation of the firms’ R&D input. Regarding our
`variable of main interest, the share of blocking citations,
`the estimated coefficient γ4 is expected to be positive,
`showing a value-premium for the share of citations that
`are “blocking” on top of the value of the total number of
`received patent citations. Similarly,
`the estimated
`coefficient γ5 is expected to be positive, showing a value-
`premium for the share of citations that are classified as
`non-infringing state of the art in a technology field.
`
`
`
`VI. CONCLUSION
`
`Innovation is considered to be a major cause
`
`of economic growth and welfare. A necessary condition
`for private innovative activity to take place is that
`innovation increases the profits of those performing R&D
`activities. This has stimulated researchers to assess the
`value of firms’ R&D activities, patents, patent citations as
`a patent value correlate (e.g. Hall et al., 2005) and
`innovation strategies (e.g. Ceccagnoli, 2009). We add to
`this literature in that we suggest to investigate differences
`in the value of patented inventions as visible in the
`purpose for which
`they are cited by
`later patent
`applications. Making use of the citation classification
`available at the EPO, patents cited in later patent
`applications because they challenge their novelty or
`inventive step (blocking citations) can be distinguished
`from patents cited as non-infringing state of the art in a
`technology field. We suggest that patents that frequently
`appear as blocking references in future patent filings (of
`other firms) are more valuable to their owners than
`patented inventions which receive mainly non-blocking
`citations. Blocking citations indicate that the cited patent
`threatens the granting of other patents, which may provide
`the owner of
`the cited patent with an
`important
`competitive advantage as the cited patent may keep
`competitors off markets and technologies, by legally
`depriving competitors from obtaining patents on related
`inventions or by narrowing the scope of their patents.
`Blocking references can refer to single patent claims so
`that a patent application can still be granted if the
`respective claim is removed or modified. Similarly,
`patents that often appear as non-infringing state of the art
`are suggested to have a higher value than the average.
`Patents receiving many cites as state of the art are
`presumably patents
`that make a very valuable
`technological contribution so that they trigger many
`follow-up inventions.
`The hypotheses of whether different citation
`types correlate to a different extent with the private value
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`[20] Hall, B.H., G. Thoma and S. Torrisi (2007). The Market
`Value of Patents and R&D: Evidence from European
`Firms. NBER Working Paper 13426, Cambridge, MA.
`[21] Harhoff, D. and M. Reitzig (2004). Determinants of
`Opposition against EPO Patent Grants – the Case of
`Biotechnology and Pharmaceuticals. International Journal
`of Industrial Organization 22: 443-480.
`[22] Harhoff, D., K. Hoisl and C. Webb (2005). European
`Patent Citations: How to Count and how to Interpret them,
`mimeo, Munich.
`[23] Harhoff, D., F. Narin, F.M. Scherer and K. Vopel (1999).
`Citation Frequency and the Value of Patented Innovation.
`Review of Economics and Statistics 81(3): 511-515.
`[24] Hedge, D. and B. Sampat (2009). Examiner Citations,
`Applicant Citations, and the Private Value of Patents.
`Economics Letters: 287-289.
`[25] Jaffe, A.B., Trajtenberg M. and M. Fogarty (2000).
`Knowledge Spillovers and Patent Citations: Evidence
`from a Survey of Inventors. American Economic Review
`90(2): 215-218.
`[26] Pakes, A. (1985). On Patents, R&D, and the Stock Market
`Rate of Return. Journal of Political Economy 93(21): 390-
`408.
`[27] Mairesse, J. and Mohnen, P. (1996). R&D-Productivity
`Growth: What have we Learned from Econometric
`Studies? Proceedings of the EUNETIC Conference on
`Evolutionari Economics of Technological Change:
`Assessment of results and new frontiers. Strassbourgh,
`October 1994, pp. 817-888.
`[28] Michel, J. and B. Bettels (2001). Patent Citation Analysis.
`Scientometrics 51: 185-201.
`[29] Schankerman, M. and A. Pakes (1996). Estimates of the
`Value of Patent Rights in European Countries during the
`Post-1950 Period. The Economic Journal 96: 1052-1076.
`[30] Scherer, F.M. (1965). Firm size, Market Structure,
`Opportunity, and the Output of Patented Inventions,”
`American Economic Review 55, 1097-1123.
`[31] Schmookler, J. (1966). Invention and Economic Growth.
`Harvard University Press: Cambridge.
`[32] Trajtenberg, M. (1990). A Penny for Your Quotes: Patent
`Citations and the Value of Innovations. RAND Journal of
`Economics 21(1): 172-187.
`[33] Webb C., H. Dernis, D., Harhoff and K. Hoisl (2005).
`Analyzing European and International Patent Citations: A
`Set of EPO Database Building Blocks. STI Working Paper
`2005/9, OECD.
`
`
`
`
`
`
`
`of patents can be investigated using the market value
`approach.
`
`
`
`REFERENCES
`
`
`[1] Albert, M.B., D. Avery, F. Narin, and P. McAllister
`(1991). Direct Validation of Citation Counts as Indicators
`of Industrially Important Patents. Research Policy 20:
`251-259.
`[2] Alcacer, J. and M. Gittelman (2006). Patent Citations as a
`Measure of Knowledge Flows: The Influence of Examiner
`Citations. Review of Economics and Statistics 88(4): 774-
`779.
`[3] Bessen, J. (2008). The Value of U.S. Patents by Owner
`and Patent Characteristics. Research Policy 37: 932-945.
`[4] Bloom, N. and J. Van Reenen (2002). Patents, Real
`Options and Firm Performance. Economic Journal 112(3):
`97-116.
`[5] Ceccagnoli, M. (2009). Appropriability, Preemption and
`Firm Performance. Strategic Management Journal 30: 81-
`98.
`[6] Criscuolo, P. and Verspagen B.(2008). Does it Matter
`where Patent Citations come from? Inventor vs. Examiner
`Citations in European Patents. Research Policy, 37, 1892-
`1908.
`[7] Czarnitzki, D., B.H. Hall and R. Oriani (2006). The
`Market Valuation of Knowledge Assets in US and
`European Firms. in: D. Bosworth and E. Webster (eds.):
`The Management of Intellectual Property, Cheltenham
`Glos: 111-131.
`[8] Czarnitzki, D., K. Hussinger and C. Schneider (2009).
`Why Challenge the Ivory Tower? New Evidence on the
`Basicness of Academic Patents, Kyklos 62: 488-499.
`[9] Czarnitzki, D. and K. Kraft (2004). Innovation Indicators
`and Corporate Credit Ratings: Evidence from German
`Firms. Economics Letters 82(3): 377-384.
`[10] Della Malva, A. and K. Hussinger (2010). Corporate
`Science in the Patent System: An Analysis of the
`Semiconductor Technology. ZEW Discussion Paper No.
`10-098, Mannheim.
`[11] Deng, Y. (2007). Private Value of European Patents.
`European Economic Review 51: 1785-1812.
`[12] Gambardella, A., D. Harhoff and B. Verspagen (2008).
`The Value of European Patents. European Management
`Review 5: 69-84.
`[13] Giuri, P., M. Mariani, S. Brusoni, G. Crespi, D. Francoz,
`A. Gambardella, W. Garcia-Fontes, A. Geuna, R.
`Gonzales, D. Harhoff, K. Hoisl, C. Lebas, A. Luzzi, L.
`Magazzini, L. Nesta, O. Nomaler, N. Palomeras, P. Patel,
`M. Romanelli and B. Verspagen (2007). Inventors and
`Invention Processes in Europe: Results from the PatVal-
`EU Survey. Research Policy 36: 1107–1127.
`[14] Griliches, Z. (1981). Market Value, R&D and Patents.
`Economics Letters 7: 183-187.
`[15] Griliches, Z. (1984). R&D, Patents and Productivity.
`University of Chicago Press, Chicago.
`[16] Griliches, Z. (1995). R&D and Productivity: Econometric
`Results and Measurement Issues. In Stoneman, P. (ed.).
`Handbook of
`the Economics of
`Innovation and
`Technological Change. Oxford, Blackwell, pp. 52-89.
`[17] Guellec, D., C. Martinez and M.P. Zuniga (2008). More
`Exclusion than Invention: Blocking Patents at Work.
`mimeo. OECD, Paris.
`[18] Hall, B.H. (2000). Innovation and Market Value. In R.
`Barrell, G. Mason and M. O’Mahoney (eds.): Productivity,
`Innovation and Economic Performance. Cambridge:
`Cambridge University Press.
`[19] Hall, B.H., A.B. Jaffe and M. Trajtenberg (2005). Market
`Value and Patent Citations, Rand Journal of Economics 36:
`16-38.
`
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`Ebay and GSI v. Landmark
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