Diversification across ASEAN-wide sectoral and national equity returns

This paper examines the effects of local and global shocks on the sector indices and national returns of the Association of Southeast Asian Nations (ASEAN) by using the univariate AR-GARCH model. We find that regional and global shocks have different influences on the ASEAN-wide sector and national equity indices. There is evidence that the ASEAN-wide sectoral returns are mostly driven by local shocks, except for the insurance and technology sectors. The volatility of Singapore's and Vietnam's national returns mostly results from their own shocks rather than local and global shocks. Applying the trend spillover model, this paper also shows that the effects of regional and global shocks on return volatility have been decreasing for almost all ASEAN-wide sectors' equity indices, while the trend for the volatility spillover effects of those shocks are positive and significant for the production and industries group sectors, as well as the food and beverage sector. Comparing the variance ratios of ASEAN sectoral and national returns, it is evident that the percentage of national equity returns belonging to their own shocks is higher than that of sectoral returns, indicating that investors might be better off diversifying their assets across countries rather than sectors in ASEAN area. This finding is consistent with the results of the mean–variance frontiers, as the portfolio composed purely of ASEAN national returns has a stronger efficiency frontier than a portfolio of all ASEAN-wide sector equity returns. By using the spanning and intersection tests, the paper also indicates that adding ASEAN national equity returns might improve the efficiency frontiers of investors' holding portfolios.