Background: The global capital markets have enlarged investment opportunities and thus also the sources of funds for companies which increasingly face global markets for their services and products. Huge capital movements show that investors are constantly searching ways to minimise risk and maximise returns. In the light of the substantial growth of assets in institutional funds, an important question for international finance is the degree to which institutional investors have diversified their portfolios internationally.

Purpose: The purpose of this study is to examine the international diversification of portfolio investments of institutional investors in Japan, the US and the UK and deepen into international diversification in portfolios of Japanese institutional investors.

Demarcations: Institutional investors can use their power directly in companies or indirectly through capital markets. In this thesis, I will not discuss corporate governance issues. Nor is it an aim of this thesis to try to find the optimal portfolio or the best performing portfolio.

Method: Secondary data in this study are based on several sources from academic literature as well as from public data and statistics. Primary data for this study include interviews and background discussions as well as my own calculations. Interviews were made in order to obtain more information and make a proper comparison. The interviews were held in Tokyo, Japan.

Conclusions: International diversification of portfolio investment of institutional investors tend to differ more between countries where the investors are based than between the type of investor in different countries. Institutional investors in UK tend to diversify their investments more internationally compared to Japanese and US counterparts. Japanese institutional investors tend to have very similar international diversification strategies. This can be explained by cultural aspects which traditionally have promoted risk averse and domestic investment strategies. Furthermore, there are reasons which make investment strategies more country contingent. Currency risk, level of knowledge and domestic investment opportunities have critical impact on international investments.