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Pioneering Inventors or Thicket Builders: Which U.S. Firms Use Continuations in Patenting?


  • Deepak Hegde

    () (Haas School of Business, University of California, Berkeley, Berkeley, California 94720)

  • David C. Mowery

    () (Haas School of Business, University of California, Berkeley, Berkeley, California 94720; and National Bureau of Economic Research, Cambridge, Massachusetts 02138)

  • Stuart J. H. Graham

    () (College of Management, Georgia Institute of Technology, Atlanta, Georgia 30332)


Why do firms use continuations in the prosecution of their patents? Motivated by the widespread use of continuations by U.S. firms and the prominence of this procedure in U.S. patent policy debates, we investigate the influence of corporate and patent characteristics on the use of continuations. We employ novel data on applicants and their filings of three types of continuations--the continuation application (CAP), the continuations in part (CIP), and divisions--during 1981-2000 to distinguish among the motives for continuing patents. We find that CIPs are disproportionately filed by research and development-intensive firms that patent heavily, and that these continuations are more common in chemical and biological technologies. Patents issuing from CIPs cover relatively important inventions and their use appears consistent with a strategy of protecting "pioneering inventions." In contrast, CAPs and divisions are associated with less important patents assigned to capital-intensive firms, particularly in computer and semiconductor fields, and appear to be used in defensive patenting strategies. We analyze the effects of the 1995 change in patent term, and find that the act reduced continuations overall and shifted the output of continuations toward less important patents.

Suggested Citation

  • Deepak Hegde & David C. Mowery & Stuart J. H. Graham, 2009. "Pioneering Inventors or Thicket Builders: Which U.S. Firms Use Continuations in Patenting?," Management Science, INFORMS, vol. 55(7), pages 1214-1226, July.
  • Handle: RePEc:inm:ormnsc:v:55:y:2009:i:7:p:1214-1226

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    References listed on IDEAS

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    Cited by:

    1. Lei, Zhen & Wright, Brian D., 2017. "Why weak patents? Testing the examiner ignorance hypothesis," Journal of Public Economics, Elsevier, vol. 148(C), pages 43-56.
    2. Crass, Dirk & Garcia Valero, Francisco & Pitton, Francesco & Rammer, Christian, 2016. "Protecting innovation through patents and trade secrets: Determinants and performance impacts for firms with a single innovation," ZEW Discussion Papers 16-061, ZEW - Zentrum für Europäische Wirtschaftsforschung / Center for European Economic Research.
    3. Andreas Panagopoulos & Kyriakos Drivas, 2016. "Using the Patent Term Changes in Assessing the Evolution of Patent Valuation from Filing to Maturity," Working Papers 1608, University of Crete, Department of Economics.
    4. Dr Chiara Rosazza Bondibene, 2012. "A Study of Patent Thickets," National Institute of Economic and Social Research (NIESR) Discussion Papers 401, National Institute of Economic and Social Research.
    5. David S. Abrams & Ufuk Akcigit & Jillian Popadak, 2013. "Patent Value and Citations: Creative Destruction or Strategic Disruption?," NBER Working Papers 19647, National Bureau of Economic Research, Inc.
    6. Bronwyn Hall & Christian Helmers & Mark Rogers & Vania Sena, 2014. "The Choice between Formal and Informal Intellectual Property: A Review," Journal of Economic Literature, American Economic Association, vol. 52(2), pages 375-423, June.
    7. Bruno van Pottelsberghe de la Potterie, 2011. "The quality factor in patent systems," Industrial and Corporate Change, Oxford University Press, vol. 20(6), pages 1755-1793, December.
    8. de Saint-Georges, Matthis & van Pottelsberghe de la Potterie, Bruno, 2013. "A quality index for patent systems," Research Policy, Elsevier, vol. 42(3), pages 704-719.
    9. Schwiebacher, Franz, 2013. "Does fragmented or heterogeneous IP ownership stifle investments in innovation?," ZEW Discussion Papers 13-096, ZEW - Zentrum für Europäische Wirtschaftsforschung / Center for European Economic Research.
    10. Dietmar Harhoff, 2016. "Patent Quality and Examination in Europe," American Economic Review, American Economic Association, vol. 106(5), pages 193-197, May.


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