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Is the International Diversification Potential Diminishing? Foreign Equity Inside and Outside the US


  • Karen K. Lewis


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.

Suggested Citation

  • Karen K. Lewis, 2006. "Is the International Diversification Potential Diminishing? Foreign Equity Inside and Outside the US," NBER Working Papers 12697, National Bureau of Economic Research, Inc.
  • Handle: RePEc:nbr:nberwo:12697
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    References listed on IDEAS

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    Cited by:

    1. Boyle, Glenn, 2009. "Capital Market Integration: A Review of the Issues and an Assessment of New Zealand's Position," Working Paper Series 4034, Victoria University of Wellington, The New Zealand Institute for the Study of Competition and Regulation.
    2. Nahil Boussiga & Ezzeddine Abaoub, 2013. "International Financial Integration And Equity Risk Premium In Emerging Countries," Journal of Applied Management and Investments, Department of Business Administration and Corporate Security, International Humanitarian University, vol. 2(1), pages 4-14.
    3. Dennis P. Quinn & Hans-Joachim Voth, 2008. "A Century of Global Equity Market Correlations," American Economic Review, American Economic Association, vol. 98(2), pages 535-540, May.
    4. Arghyrou, Michael G. & Gregoriou, Andros & Kontonikas, Alexandros, 2009. "Do real interest rates converge? Evidence from the European union," Journal of International Financial Markets, Institutions and Money, Elsevier, vol. 19(3), pages 447-460, July.
    5. Quinn, Dennis & Voth, Hans-Joachim, 2008. "Free Flows, Limited Diversification: Explaining the Fall and Rise of Stock Market Correlations, 1890-2001," CEPR Discussion Papers 7013, C.E.P.R. Discussion Papers.
    6. Ching-Chuan Tsong & Cheng-Feng Lee, 2013. "Further Evidence On Real Interest Rate Equalization: Panel Information, Non-Linearities And Structural Changes," Bulletin of Economic Research, Wiley Blackwell, vol. 65, pages 85-105, May.
    7. Chi-Hsiou Hung, 2007. "Return Explanatory Ability and Predictability of Non-Linear Market Models," Working Papers 2007_05, Durham University Business School.

    More about this item

    JEL classification:

    • F3 - International Economics - - International Finance
    • F4 - International Economics - - Macroeconomic Aspects of International Trade and Finance
    • G11 - Financial Economics - - General Financial Markets - - - Portfolio Choice; Investment Decisions
    • G15 - Financial Economics - - General Financial Markets - - - International Financial Markets

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