Theoretical basis of investments and investment activity research
Authors: Sandulskyi R. 
Published: July 2024

The article is devoted to the generalization of the main provisions of the leading economic theories in the field of investment, the main stages of the development of the investment process research theory are systematized. The purpose of the article is to study the evolution and systematization of the theoretical foundations that reveal the essence of investment relations, and their deepening of the theory in the context of the concept of sustainable development actualization, the knowledge economy, and the formation of the information economy.
It has been proven that there is a close internal connection between investments and innovations, leading investments in ensuring economic growth and the transition to the technological structure of Industry 4.0, implementing structural and institutional transformations, digitizing the investment process, overcoming the negative impact of the Covid-19 pandemic, military conflicts, etc.
The author critically reviewed the position of the leading economic schools in the field of investment and made a conclusion regarding the development of the investment activity research theory, as well as changes in the investment behavior of business entities. The methodological approaches of the classical, neoclassical, Keynesian, and institutional economic schools, which are set forth in the theories of investment and accumulation, are systematized, revealing the issue of the investment process transformation under the influence of endogenous and exogenous factors.
It was concluded that the investment process of reproduction of social capital, on which economic development is based, changes within the historical transformation of the entire system of economic relations, which led to the improvement of investment quality in accordance with the challenges of the economy industrial development. It has been proven that the system-synergistic methodology has the highest level of validity and effectiveness for researching the investment category, as it allows to deepen the understanding of the investment category.
The author emphasizes that the system-synergistic methodology takes into account the information and ecosystem nature of the modern investment process, which reflects the non-linear trends of movement and development of the economic system, and is also a mechanism for innovation by business entities. It is substantiated that investment is an independent economic category, which represents the process of accumulation and extended reproduction of social capital, which are considered as a single integrated complex system. It is argued that investments represent a complex multi-level, multi-subject and multi-object system of relations regarding the accumulation of social capital in the national economy.
It has been proven that the development of investment processes at the macro-, meso-, and micro levels in modern conditions requires the creation of an appropriate ecosystem for the organization of the investment process, the effective functioning of which is achieved under the condition of full satisfaction of all stakeholders interests. It was highlighted that in the context of the actualization of the sustainable development concept, circular and green economy, it is necessary to ensure the implementation of sustainable investment in order to increase socially responsible economic development based on ESG development standards.
Key words: investment theories, investment process, investment, investment ecosystem, sustainable investment, digitalization.