MPT

モダンポートフォリオ理論（MPT）

モダン・ポートフォリオ理論 (MPT) is a financial model developed by economist Harry Markowitz in the 1950s. It provides a framework for constructing a portfolio of assets in a way that maximizes 期待リターン for a given level of risk, or alternatively minimizes risk for a given level of expected return. The theory is based on the principle of diversification, which suggests that a well-diversified portfolio can reduce unsystematic risk—the risk associated with individual assets.

MPT introduces the concept of the ‘efficient frontier,’ which is a graphical representation of the optimal portfolios that offer the highest expected return for a defined level of risk. Investors are encouraged to select portfolios that lie on this frontier to achieve the best possible risk-return trade-off. The theory also emphasizes the importance of considering the correlation between asset returns; assets that do not move in relation to each other can help reduce overall portfolio risk.

MPTの主要な構成要素は次の通りです：

• 期待リターン： The anticipated return on an investment, typically calculated as a weighted average of the expected returns of the individual assets in the portfolio.
• リスク（ボラティリティ）： Often measured by the standard deviation of returns, indicating how much the returns of an asset deviate from its 期待リターン。
• 相関： A statistical measure that describes the degree to which two assets move in relation to each other.

MPTは、金融の分野で影響力を持ってきました finance, it also has limitations, including assumptions of rational investor behavior and market efficiency. Despite these drawbacks, it remains a foundational theory in 投資管理 and portfolio construction.