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Characterizing Informational Barriers To Entry In The Anti-Ulcer Drug Market

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  • Matthew Shum

Abstract

We empirically quantify and characterize informational barriers to entry into the anti-ulcer drug market by studying the diffusion process of the molecule Omeprazole in the first 30 months after it entered the market. Using a novel panel dataset tracking doctors' complete prescription histories, we specify and estimate a learning model in which doctors, initially uncertain about the quality differential between Omeprazole and the incumbent molecules, update their beliefs about this differential from first-hand experience after observing noisy signals from patients to whom they have prescribed the molecule. We find strong evidence that doctors' uncertainty about Omeprazole's quality is resolved by first-hand experience rather than through the pharmaceutical companies' marketing activities, so that learning through first-hand experience explains almost all of Omeprazole's diffusion path over our three-year sample period. This casts some doubt on previous researchers' findings, utilizing aggregate data, regarding the importance of marketing in securing market share for an entrant brand.

Suggested Citation

  • Matthew Shum, 1998. "Characterizing Informational Barriers To Entry In The Anti-Ulcer Drug Market," Working Papers mshum-98-03, University of Toronto, Department of Economics.
    • Handle: RePEc:tor:tecipa:mshum-98-03
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    References listed on IDEAS

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    1. Sara Ellison Fisher & Iain Cockburn & Zvi Griliches & Jerry Hausman, 1997. "Characteristics of Demand for Pharmaceutical Products: An Examination of Four Cephalosporins," RAND Journal of Economics, The RAND Corporation, vol. 28(3), pages 426-446, Autumn.
    2. Berndt, Ernst R. & Pindyck, Robert S. & Azoulay, Pierre, 1970-, 1998. "Network effects and diffusion in pharmaceutical markets : antiulcer drugs," Working papers WP 4059-98., Massachusetts Institute of Technology (MIT), Sloan School of Management.
    3. Steven Berry & James Levinsohn & Ariel Pakes, 2004. "Differentiated Products Demand Systems from a Combination of Micro and Macro Data: The New Car Market," Journal of Political Economy, University of Chicago Press, vol. 112(1), pages 68-105, February.
    4. Bagwell, Kyle, 1990. "Informational product differentiation as a barrier to entry," International Journal of Industrial Organization, Elsevier, vol. 8(2), pages 207-223, June.
    5. Schmalensee, Richard, 1982. "Product Differentiation Advantages of Pioneering Brands," American Economic Review, American Economic Association, vol. 72(3), pages 349-365, June.
    6. Ali Fekrat, M. & Inclan, Carla & Petroni, David, 1996. "Corporate environmental disclosures: Competitive disclosure hypothesis using 1991 annual report data," The International Journal of Accounting, Elsevier, vol. 31(2), pages 175-195.
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    Cited by:

    1. Andrew Ching, 2000. "Dynamic Equilibrium in the US Prescription Drug Market After Patent Expiration," Econometric Society World Congress 2000 Contributed Papers 1242, Econometric Society.

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    More about this item

    Keywords

    pharmaceutical industry; barriers to entry; simulated maximum likelihood; diffusion models;
    All these keywords.

    JEL classification:

    • I10 - Health, Education, and Welfare - - Health - - - General
    • L15 - Industrial Organization - - Market Structure, Firm Strategy, and Market Performance - - - Information and Product Quality
    • L65 - Industrial Organization - - Industry Studies: Manufacturing - - - Chemicals; Rubber; Drugs; Biotechnology; Plastics
    • M3 - Business Administration and Business Economics; Marketing; Accounting; Personnel Economics - - Marketing and Advertising

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