Oxera works with highly skilled independent experts who have a wealth of knowledge within their fields. These individuals are highly recognised within a variety of sectors and our collaboration with them means that we can offer the best advice, which in turn inspires our clients to make informed decisions.


Subal is a world-renowned expert in productivity and performance measurement, with particular emphasis on the theory and application of stochastic frontier analysis (SFA). He has been working in the area of efficiency and productivity for the last 25 years, and has measured performance for a variety of industries such as energy, post, transport, water, agriculture, manufacturing, banking and school systems.

He is a Distinguished University Professor at the State University of New York at Binghamton, where he teaches theoretical and applied econometrics and statistics courses at both undergraduate and postgraduate level. Subal is a highly sought-after keynote speaker at the international productivity and efficiency conferences. He is also the co-author of the highly influential book Stochastic Frontier Analysis, and lead developer of SFA software.

Selected project experience

  • Advice on efficiency issues for an electricity DNO for RIIO-ED1 (2011–12)
  • Assistance in developing a cost forecasting framework, including a benchmarking study, for a top-ten international airport (2011–12)
  • Expert advice for South Staffs Water for the Competition Commission merger inquiry with Cambridge Water (2011–12)
  • Advice on efficiency issues for a Belgian energy distribution network (2011–12)
  • Advice to a UK gas distribution company on its Business Plan submission for the RIIO-GD1 regulatory review (2011–12)
  • Advice to a European Energy Regulator on alternative performance assessment approaches in electricity and gas networks (2010–12)
  • Helped major GB bus operators to critique the impact of a change in the concessionary fares regime, including the efficient incremental costs (2010)
  • Advice during Oxera’s review of the GB rail industry’s demand forecasting framework for the UK Department for Transport (2008–10)
  • Strategic advice and performance assessments in the bus and train sectors (2008–10)
  • Provided advice for the ORR’s ‘Recommendations on how to model efficiency for future price reviews’ (2009)
  • Critique of the efficiency approaches used to benchmark BT (2008)
  • Expert advice during the Mid Kent–South East Water Competition Commission merger inquiry, including representations at hearings (2006–07)
  • Advised Royal Mail on its relative efficiency assessment (2005–06)

Selected publications

Subal is on the editorial boards of the following journals: Technological Forecasting and Social Change, Empirical Economics, Journal of Productivity Analysis, International Journal of Business and Economics, International Journal of Economic Research. He is frequently invited as a keynote speaker in various productivity and efficiency workshops throughout Europe and Asia.

  • Kumbhakar, S., Wang, H.-J. and Horncastle, A. (forthcoming), A Practitioner’s Guide to Stochastic Frontier Analysis, Cambridge University Press.
  • Kumbhakar, S. and Horncastle, A. (2010), ‘Improving the Econometric Precision of Regulatory Models’, Journal of Regulatory Economics 38:2, October, pp. 144–66.
  • Das, A. and Kumbhakar, S. (2010), ‘Productivity and Efficiency Dynamics in Indian Banking: An Input Distance Function Approach Incorporating Quality of Inputs and Outputs’, Journal of Applied Econometrics, August.
  • Poghosyan, T. and Kumbhakar, S. (2010), ‘Heterogeneity of Technological Regimes and Banking Efficiency in Emerging Economies’, Journal of Productivity Analysis 33:1, pp. 19–32.
  • Bhaumik, S.K. and Kumbhakar, S. (2010), ‘Impact of Reforms on Plant-Level Productivity and Technical Efficiency: Evidence from the Indian Manufacturing Sector’, Journal of Asian Economics, 21:2, pp. 219–32.
  • Kumbhakar, S. and Bokusheva, R. (2009), ‘Modelling Farms’ Production Decisions under Expenditure Constraints’, European Review of Agricultural Economics, 36:3, pp. 343–67.
  • Kumbhakar, S. and Parmeter, C. (2009), ‘Estimation of Hedonic Price Functions with Incomplete Information’, Empirical Economics, 39:1.
  • Kumbhakar, S. (2010), ‘Efficiency and Productivity of World Health Systems: Where Does Your Country Stand?’, Applied Economics 42:13, May, pp. 1641–59.
  • Asaftei, G., Kumbhakar, S. and Mantescu, D. (2008), ‘Ownership, Business Environment and Productivity Change’, Journal of Comparative Economics 36:3, pp. 498–509.
  • Kumbhakar, S. and Knox Lovell, C.A. (2000), Stochastic Frontier Analysis, Cambridge University Press, March.
  • Orea, L., Rodríguez-Álvarez, A. and Kumbhakar, S. (2009), ‘Explaining Occupancy Rates in the European Railways: A Reduced-Form Approach’, pp. 63–86, in N.P. Scott (ed.), Railway Transportation: Policies, Technology and Perspectives.
  • Kumbhakar, S., Orea, L., Rodríguez-Álvarez, A. and Tsionas, E.G. (2007), ‘Do We Estimate an Input or an Output Distance Function? An Application of the Mixture Approach to European Railways’, Journal of Productivity Analysis, 27:2, pp. 87–100.
  • ‘Kumbhakar, S., Park, B.U., Simar, L. and Tsionas, E.G. (2007), ‘Nonparametric Stochastic Frontiers: A Local Maximum Likelihood Approach’, Journal of Econometrics, 137:1, pp. 1–27, March.
  • Henderson, D.J. and Kumbhakar, S. (2006), ‘Public and Private Capital Productivity Puzzle: A Nonparametric Approach’, Southern Economic Journal, 73, pp. 219–32.


  • PhD Economics, University of Southern California, Los Angeles
  • Masters of Arts Economics, University of Southern California, Los Angeles
  • Masters of Arts Economics, Calcutta University, Calcutta, India