Over the past two decades international markets have become more open, leading to a common perception that global capital markets have become more integrated. In this paper, I ask what this integration and its resulting higher correlation would imply about the diversification potential across countries. For this purpose, I examine two basic groups of international returns: (1) foreign market indices and (2) foreign stocks that are listed and traded in the US. I examine the first group since this is the standard approach in the international diversification literature, while I study the second group since some have argued that US-listed foreign stocks are the more natural diversification vehicle (Errunza et al (1999)). In order to consider the possibility of shifts in the covariance of returns over time, I extend the break-date estimation approach of Bai and Perron (1998) to test for and estimate possible break dates across returns along with their confidence intervals. I find that the covariances among country stock markets have indeed shifted over time for a majority of the countries. But in contrast to the common perception that markets have become significantly more integrated over time, the covariance between foreign markets and the US market have increased only slightly from the beginning to the end of the last twenty years. At the same time, the foreign stocks in the US markets have become significantly more correlated with the US market. To consider the economic significance of these parameter changes, I use the estimates to examine the implications for a simple portfolio decision model in which a US investor could choose between US and foreign portfolios. When restricted to holding foreign assets in the form of market indices, I find that the optimal allocation in foreign market indices actually increases over time. However, the optimal allocation into foreign stocks decreases when the investor is allowed to hold foreign stocks that are traded in the US. Also, the minimum variance atta

Over the past two decades international markets have become more open, leading to a common perception that global capital markets have become more integrated. In this paper, I ask what this integration and its resulting higher correlation would imply about the diversification potential across countries. For this purpose, I examine two basic groups of international returns: (1) foreign market indices and (2) foreign stocks that are listed and traded in the US. I examine the first group since this is the standard approach in the international diversification literature, while I study the second group since some have argued that US-listed foreign stocks are the more natural diversification vehicle (Errunza et al (1999)). In order to consider the possibility of shifts in the covariance of returns over time, I extend the break-date estimation approach of Bai and Perron (1998) to test for and estimate possible break dates across returns along with their confidence intervals. I find that the covariances among country stock markets have indeed shifted over time for a majority of the countries. But in contrast to the common perception that markets have become significantly more integrated over time, the covariance between foreign markets and the US market have increased only slightly from the beginning to the end of the last twenty years. At the same time, the foreign stocks in the US markets have become significantly more correlated with the US market. To consider the economic significance of these parameter changes, I use the estimates to examine the implications for a simple portfolio decision model in which a US investor could choose between US and foreign portfolios. When restricted to holding foreign assets in the form of market indices, I find that the optimal allocation in foreign market indices actually increases over time. However, the optimal allocation into foreign stocks decreases when the investor is allowed to hold foreign stocks that are traded in the US. Also, the minimum variance attainable by the foreign portfolios has increased over time. These results suggest that the benefits to diversification have declined both for stocks inside and outside the US.

One possible explanation for home bias is that investors may obtain indirect international diversification benefits by investing in multinational firms rather than by investing directly in foreign markets. This paper employs mean-variance spanning tests to examine the diversification potential of multinational firms and foreign market indices for investors domiciled in Canada, France, Germany, Italy, Japan, the United Kingdom and the United States. We find that in most countries and most time periods, the portfolio of domestic stocks spans the risk and return opportunities of a portfolio that includes domestic and multinational stocks. However, there is weak evidence that U.S. multinationals provided global diversification benefits in the full 1984-92 sample and in the post-1987 subsample. We also find that the addition of foreign market indices to a domestic portfolio - inclusive of multinationals - provides diversification benefits. The economic importance of the shift of the portfolio frontier - measured as the utility gain from diversification - varies considerably from market to market and often reflects the benefits of large short positions in certain markets.

One possible explanation for home bias is that investors may obtain indirect international diversification benefits by investing in multinational firms rather than by investing directly in foreign markets. This paper employs mean-variance spanning tests to examine the diversification potential of multinational firms and foreign market indices for investors domiciled in Canada, France, Germany, Italy, Japan, the United Kingdom and the United States. We find that in most countries and most time periods, the portfolio of domestic stocks spans the risk and return opportunities of a portfolio that includes domestic and multinational stocks. However, there is weak evidence that U.S. multinationals provided global diversification benefits in the full 1984-92 sample and in the post-1987 subsample. We also find that the addition of foreign market indices to a domestic portfolio - inclusive of multinationals - provides diversification benefits. The economic importance of the shift of the portfolio frontier - measured as the utility gain from diversification - varies considerably from market to market and often reflects the benefits of large short positions in certain markets.

How important is foreign diversification? In this paper, we re-examine this question motivated by findings from the literature about foreign companies that are listed on US exchanges. Specifically, domestic portfolios including cross-listed stocks can provide the same diversification as foreign market returns without the need for US investors to go abroad. At the same time, the betas of these foreign stock returns against the US market increase after cross-listing, suggesting diversification worsens over time. In this paper, we assess the impact of these changes on foreign diversification for a US investor. We test for and estimate breaks in the sensitivity of individual foreign stocks listed on US exchanges. We find that roughly half of the changes in betas arise from greater integration between the U.S. and the companies' home markets, not in the companies betas themselves. Moreover, the gains from diversifying into these stocks has declined over time -- National Bureau of Economic Research web site.