Financing the green projects: Market efficiency and volatility persistence of green versus conventional bonds, and the comparative effects of health and financial crises

The establishment of the green bond market is an attempt to attain environmental sustainability from the finance perspective. One of the factors that could either hinder or promote this course is the degree of market efficiency of the market. Against this background, this study comparatively examines the market efficiency of the U.S. green and conventional bonds. In addition, the performance of both markets is investigated during global health and financial crises. Applying the fractional integration technique, we find that the overall green and conventional bonds markets are still inefficient, indicating that green and conventional investors can make excess gains by predicting the future trends of bond prices. There is also evidence that the green bond market exhibits higher volatility persistence during the global health crisis than during the global financial crisis. These findings are corroborated by the GARCH-based models, whose results show that volatility shocks are more persistent in the green bond market during the health crisis than during the financial crisis. However, the conventional bond market observes persistence in volatility shocks during both events. Towards sustainable environment goals, these results have relevant implications for green investors and policy makers.