Are green bonds a different asset class? Evidence from time-frequency connectedness analysis

Abstract

This paper investigates the time-frequency connectedness across the global green bond market and several mainstream financial and energy markets in an attempt to figure out whether green bonds represent a different asset class. The connectedness methodology proposed by Baruník and Křehlík (2018) is employed for that purpose. This approach enables quantifying the dynamics of connectedness in terms of return and volatility over time and across time scales simultaneously. The empirical results indicate that connectedness between the global green bond market and the conventional financial and energy markets mainly occurs at shorter time horizons, suggesting that shocks are rapidly transmitted across markets with an effect lasting less than a week. A strong connectedness in return and volatility is found between green bonds and Treasury and investment-grade corporate bonds, principally because of the numerous characteristics they share. This finding implies that green fixed-income securities are not a different asset class, but they closely mirror the performance of government and high-quality corporate bonds. In contrast, there is a quite limited connectedness between the green bond market and the general stock market, the renewable energy equity sector and the crude oil market regardless of the time horizon considered. This evidence shows that green bonds appear as a valuable tool to fight against climate change without having to sacrifice part of the return generated by traditional assets, particularly ordinary bonds. Furthermore, it can have useful implications for investors and policy makers.