Research on Portfolio Investment in the Risky U.S. Stock Market Based on the Mean-Variance Model

Against the backdrop of a thriving securities market and economy, there is a growing demand among investors for stock portfolio models in risky markets. This paper explores the application of the mean-variance model in this context, aiming to assist investors in making more informed investment decisions in an uncertain market. Through an in-depth analysis of the mean-variance model, the main conclusion of this paper is that certain stocks, such as AAPL, receive a higher investment proportion due to their lower risk and stable expected returns. In contrast, some high-risk or low-expected-return stocks, such as SBUX, MSFT, and QCOM, hold a smaller or zero proportion in the portfolio. This conclusion highlights the importance of balancing risk and return when constructing a portfolio and provides investors with specific asset allocation recommendations. It can help them effectively control risk while pursuing maximum returns, thereby achieving long-term stable investment gains.