Review of fuzzy investment research considering modelling environment and element fusion

Reasonable investment strategies are of great importance for investors, companies, or even countries. Therefore, many investment methods have been proposed to assist people with their investment decision-makings. In this paper, we focus on qualitative investment methods, namely fuzzy investment theory, and provide an overview of the related studies via numerical analysis and literature review. As for the numerical analysis, the status quo and evolution track of fuzzy investment research are presented from static and dynamic perspectives. Specifically, the main publish stages, the whole development trend and the theory diffusion paths of this field are provided in detail. Regarding the literature review, we summaries the fuzzy investment models with consideration of diverse fuzzy environments such as the interval-valued fuzzy, intuitionistic fuzzy, and hesitant fuzzy environments. Various elements fused in the fuzzy investment models such as risk factor, decision-making technique, and portfolio construction are introduced and overviewed as well. Furthermore, we demonstrate the corresponding practical applications of the fuzzy investment methods and clarify their application processes. This study would be helpful for readers, investors, and researchers to comprehensively learn and apply the fuzzy investment theory, which is an effective tool to fuse their subjective opinions into real investment decision-makings.