The Pollution Outsourcing Hypothesis: An empirical test for Japan

本論文では、日本の製造業企業においてアウトソーシングがどのように汚染排出比率を変化させたのかを検証した。2009年から2013年までの企業データを用いて、マッチング(PSM)などノンパラメトリック推計を用いて、アウトソーシングとCO₂排出集約度との関係を検証した。結果、アウトソーシングを始めることで汚染集約度は平均で5%低くなる。その後、1年、2年と経過するごとに6%、9%とさらに低下する。海外アウトソーシングと国内アウトソーシングに分解して分析した結果、海外アウトソーシングのほうが汚染集約度の低下に大きな寄与があったことが分かった。輸入の開始と輸出の開始に関しても同様の分析を行った結果、輸入に関してはある程度効果があるが、輸出の開始は汚染集約度に有意な結果をもたらさないことが分かった。

This paper investigates whether firms that engage in outsourcing improve their environmental performance using Japanese firm-level data for the period 2009-2013. To identify the causal effect of production outsourcing on firm carbon dioxide (CO₂) emission intensities, we employ a non-parametric approach combining propensity score matching (PSM) and difference-in-differences (DiD). Our results show that, relative to the control group, the growth in CO₂ emission intensities (relative to the year before treatment) of new production outsourcers is 5.1% lower in the year when they start outsourcing, and 6.6% and 9.5% lower one and two years after outsourcing, respectively. When we decompose firms' outsourcing activities into domestic and foreign according to the destination of the outsourced production, we find that the effects on emission intensity growth are driven by overseas outsourcing. Firms that outsource part(s) of their production overseas have a 7.3% lower emission intensity growth when they start outsourcing and a 7.7% reduction in the following year. We also investigate whether the decision to import or export has an impact on firm level environmental performance as predicted by the more traditional pollution halo hypothesis (PHH) literature. Firms are found to have a 3.3% lower growth rate of CO₂ emission intensity when they start to import, but no significant impact is found for exporting.