Sugata Marjit, Lei Yang, School of Economics Discussion Paper No. 544 April 2015, Centre for Studies in Social Sciences, Calcutta, Hong Kong Polytechnic University, Hong Kong.

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This paper investigates the optimal environmental policy (the mix of emissions tax and R&D subsidy) when two firms, producing differentiated products, compete in the output market over time. Firms compete over supply schedules, which encompasses a continuum of market structures from Bertrand to Cournot. While production generates environmentally damaging emissions, firms can undertake R&D, which has the sole purpose of reducing emissions. In addition to characterising the optimal policy, we examine how the optimal tax and subsidy and the optimal level of abatement change as competition intensifies, as the dynamic parameters change and as the investment in abatement technology changes. In this setting, increased competition no longer necessarily leads to an increase in welfare. Instead, there are two forces. Competition increases welfare through its impact on the final goods price. However, lower prices result in larger quantities and more pollution. Our contribution is to show that the impact depends on the extent of the market, and the nature of preferences and technology.