Home Media Research Seminar Teaching Vita Voucher


For copies of papers please follow links below, see Google Scholar, or E-mail david.ridley((at))duke.edu

I am interested in innovation, location, and pricing, especially in health care.


In 2006 we proposed a priority review voucher (Ridley et al. 2006) to encourage innovation for neglected diseases. In 2007 it became law. You can read more about the priority review voucher on Wikipedia or on my voucher page.

  1. David B. Ridley, Henry G. Grabowski, and Jeffrey L. Moe. "Developing Drugs for Developing Countries." Health Affairs. 2006. Vol. 25, No. 2: 313-324. Appendix (Working paper)
  2. Jeffrey L. Moe, Henry G. Grabowski, David B. Ridley, and Aaron S. Kesselheim. "FDA Review Vouchers." Correspondence in The New England Journal of Medicine. 2009. Vol. 360, No. 8: 837-838.
  3. Henry G. Grabowski, David B. Ridley, and Jeffrey L. Moe. "Priority Review Vouchers to Encourage Innovation for Neglected Diseases." In: K. Eggleston, ed. Prescribing Cultures and Pharmaceutical Policy in the Asia-Pacific. Brookings Institution Press. 2009.
  4. David B. Ridley and Alfonso Calles Sanchez. "Introduction of European Priority Review Vouchers to Encourage Development of New Medicines for Neglected Diseases." The Lancet. 2010. Vol. 376, No. 9744: 922-927. (Working paper)
  5. Adrian Towse, Eric Keuffel, Hannah E. Kettler and David B. Ridley. "Drugs and Vaccines for Developing Countries." In: P. Danzon and S. Nicholson, eds. Oxford Handbook of the Economics of the Biopharmaceutical Industry. 2012. (Working paper)
  6. Joshua S. Gans and David B. Ridley. "Innovation Incentives under Transferable Fast-Track Regulatory Review." Journal of Industrial Economics. 2013. Vol. 61, No. 3: 789-816. (Working paper)


How sensitive is demand to copayments and advertising? How does competition affect generic prices? Do Americans pay higher prices for pharmaceuticals than people in other rich countries? How can we encourage lower prices for poor countries?

  1. David B. Ridley and Kevin A. Schulman. "Differential Pricing of Pharmaceuticals in the Internet Age." Journal of Ambulatory Care Management. 2004. Vol. 27, No. 3: 210-214.
  2. David B. Ridley. "Price Differentiation and Transparency in the Global Pharmaceutical Marketplace." Pharmacoeconomics. 2005. Vol. 23, No. 7: 651-658.
  3. David B. Ridley and Kirsten Axelsen. "Impact of Medicaid Preferred Drug Lists on Therapeutic Adherence." Pharmacoeconomics. 2006. Vol. 24, Suppl. 3: 65-78.
  4. Henry G. Grabowski, David B. Ridley, and Kevin A. Schulman. "Entry and Competition in Generic Biologics." Managerial and Decision Economics. 2007. Vol. 28: 439-451. (Working paper)
  5. David B. Ridley. "International Price Comparisons for Novel and Follow-On Drugs." Value in Health. 2007. Vol. 10, No. 6: 510-511. (Working paper)
  6. Margaret K. Kyle and David B. Ridley. "Would Greater Transparency and Uniformity of Health Care Prices Benefit Poor Patients?" Health Affairs. 2007. Vol. 26, No. 5: 1384-1391. (Working paper)
  7. Peter Arcidiacono, Paul Ellickson, Peter Landry, and David B. Ridley. "Pharmaceutical Followers." International Journal of Industrial Organization. 2013. Vol. 31, No. 5: 538–553 (NBER working paper)
    Paul Geroski Award for one of the two best papers in the journal that year.
  8. David B. Ridley. "Payments, Promotion, and the Purple Pill." Health Economics. 2015. Vol. 24, No. 1: 86-103. (Working paper)
  9. Stephane A. Regnier and David B. Ridley, "Forecasting Market Share in the United States Pharmaceutical Market." Nature Reviews Drug Discovery. Forthcoming.

Health Care Costs

How costly is post-approval drug safety? How costly is hospital inefficiency?

  1. Bimal R. Shah, Shelby D. Reed, Jennifer Francis, David B. Ridley, and Kevin A. Schulman. "The Cost of Inefficiency: A Look at US Hospital Overhead Costs from 1985-1997." Journal of Health Care Finance. 2003. Vol. 30: 1-9.
  2. David B. Ridley, Judith M. Kramer, Hugh H. Tilson, Henry G. Grabowski, and Kevin A. Schulman. "Spending on Postapproval Drug Safety." Health Affairs. 2006. Vol. 25, No. 2: 420-428. (Working paper)


When firms cluster, they engage in more intense price competition. So why cluster? My research explores some hypotheses. Followers cluster near leaders to i) free ride on the demand information of the market leader, ii) because they can differentiate their products and mitigate price competition, and iii) because zoning forces clustering.

  1. David B. Ridley. "Herding versus Hotelling: Market Entry with Costly Information." Journal of Economics and Management Strategy. 2008. Vol. 17, No. 3: 607-631. (Working paper)
  2. Gabriel A. Picone, David B. Ridley, and Paul A. Zandbergen. "Distance Decreases with Differentiation: Strategic Agglomeration by Retailers." International Journal of Industrial Organization. 2009. Vol. 27, No. 3: 463-473. (Working paper)
  3. David B. Ridley. "Hotelling's Law." In D. Teece and M. Augier, eds. The Palgrave Encyclopedia of Strategic Management. 2013. (Working paper)
  4. David B. Ridley, Frank A. Sloan, and Yan Song. "Retail Zoning and Competition." (Working paper)