اثرات زیست محیطی انتشار هواپیما و مالیات بر سوخت هواپیما در ژاپن   Environmental impact of aircraft emissions and aviation fuel tax in Japan

1. Introduction Aviation is a vital component of most economies and it represents one of the greatest developments of the 20th Century. There is an indisputable expectation that the industry will continue to grow, particularly given the rapid development of low-cost carriers. It is anticipated that the amount of CO2 emissions related to aviation will also increase rapidly, keeping pace with the expansion of the industry. Given the constraints on CO2 emissions are becoming tighter, as evidenced by the agreement of the Paris Climate Change Conference in 2015, it is crucial that the implications of the expansion of aviation with regard to global CO2 emissions, and the effects of an incentive-based tool represented by a fuel tax for reducing CO2 emissions, should be evaluated carefully. To the best of the authors’ knowledge, however, there have been relatively few studies exploring the effectiveness of jet fuel tax on the reduction of aircraft CO2 emissions. The purpose of the present paper is to address this problem by analysing data relevant to the aviation fuel tax adopted in Japan. Specifically, it investigates the effects of a reduction in aviation fuel tax on CO2 emissions by the aviation sector. Because of the 30% reduction in tax implemented by the Japanese government in April 2011, it is possible for us to compare the amount of CO2 emissions before and after the tax adjustment. We find that the amount of CO2 emissions from Japanese domestic flights would increase signifi- cantly compared with a situation where such a tax reduction was not implemented, reflecting the effectiveness of fuel tax for reducing CO2 emissions by aircraft. This finding is of great importance because an increase in the amount of CO2 emissions is considered unavoidable, especially in a region that has a rapidly expanding airline market. We investigated the Aviation Fuel Tax of Japan (koukuukinenryouzei) by considering both its impact on the national demandfor aviation fuel and its indirect contribution to Japan’s environmental efforts for reducing the amount of CO2 emissions, using a Bayesian time series approach that contrasted the results before and after the 30% tax reduction. Through the application of causal impact analysis, based upon Brodersen et al. (2015), this study constructed a scenario that predicted the market’s response in the absence of the tax reduction, which allowed an estimation of the quantity of additional fuel consumed between April 2011 and December 2013. Thus, we estimated the causal impact of the 30% reduction in the aviation fuel tax, which to the best of our knowledge, has not been undertaken before.