Optimization of Stock Portfolio Investment on the IDXHIDIV20 Index Using the Single Index Model and Markowitz Model Approach for Beginner Investors

Abstract

Purpose - This study investigates the construction of optimal stock portfolios using the Single Index Model (SIM) and the Markowitz Mean-Variance Model (MM), applied to the IDX High Dividend 20 (IDXHIDIV20) index. With a growing number of novice investors in Indonesia, understanding which classical model offers better guidance for dividend-oriented investing is increasingly essential.

Design/methodology/approach - A descriptive quantitative approach was used, employing weekly secondary data of 20 IDXHIDIV20 constituents from 2019 to 2024. The SIM was applied through regression-based estimations and excess return-to-beta ranking, while the Markowitz Model utilized a full variance-covariance matrix with Excel Solver optimization.

Originality -  This research contributes empirical evidence to modern portfolio theory by comparing the effectiveness of SIM and MM in the context of novice investors in emerging markets. It also incorporates the relevance of sustainability factors through dividend strategies.

Findings and Discussion - The Markowitz portfolio consistently outperforms the SIM portfolio in both return and risk dimensions, achieving an expected annual return of 23.56% with a standard deviation of 2.81%, compared to SIM's 22.96% return with 5.89% volatility. While the SIM offers practical simplicity for novice investors, the MM provides superior diversification through covariance-based optimization. These findings validate the importance of robust model selection in portfolio strategy.

Conclusion - The Markowitz Model is preferable for investors with access to analytical tools and data due to its superior risk-return performance, while SIM remains a valuable approach for those with limited resources. The study enhances financial education and supports informed investment decisions for dividend-focused strategies in emerging markets.