Internationalizing the Domestic Portfolio The domestic investor may choose among a set of individual securities in the domestic market. The near-infinite set of portfolio combinations of domestic securities form the domestic portfolio opportunity set (next exhibit). The set of portfolios along the extreme left edge of the set is termed the efficient frontier. This efficient frontier represents the optimal portfolios of securities that possess the minimum expected risk for each level of expected portfolio return.Internationalizing the Domestic Portfolio The domestic investor may choose among a set of individual securities in the domestic market. The near-infinite set of portfolio combinations of domestic securities form the domestic portfolio opportunity set (next exhibit). The set of portfolios along the extreme left edge of the set is termed the efficient frontier. This efficient frontier represents the optimal portfolios of securities that possess the minimum expected risk for each level of expected portfolio return