Benefits of International Bond Diversification

Abstract

This paper assesses the incremental diversification benefits to US investors from investing in international government bonds. In light of suggestions that these benefits have fallen sharply in the recent decade due to more closely synchronized business cycles, we use mean-variance spanning tests to show that currency-hedged bonds provide significant diversification benefits over the period from January 1992 to September 2002. Using a bivariate GARCH framework, we find that US bond returns have become increasingly correlated with UK and German bond returns, but have experienced declining correlations with Japanese bonds. The changing correlations are consistent with variation in the synchronization of business cycles. However, the evidence suggests that correlations have not become high enough to threaten the gains from diversification and that these gains on a currency-hedged basis are not diminished during periods of weakness or increased volatility in US or foreign bond markets. Conditional Sharpe ratios also demonstrate that risk-reward tradeoffs for each bond market vary in a predictable manner, which further underscores the potential benefits of international bond investing. Finally, we demonstrate how conditional yield betas and conditional yield beta adjusted foreign bond durations can be constructed from our model estimates.

Keywords: International bonds, conditional correlation, bond correlation, yield beta, return beta, diversification benefits, mean-variance spanning

JEL Classification: G15