This paper deals with retrial queues of the |MQ/M/c/∞|- type in which the rate of input flow depends on the number of sources of repeated calls and each call has only one retrial attempt. That is, if a call fails to enter the server facility at the retrial attempt, then it leaves the system without service. The existence conditions of stationary regime and the vector-matrix of the stationary probabilities of the service process are represented. This representation uses an approximation of the initial model by means of the truncated one and the directs passage to the limit. For these systems a threshold strategy for the rate of input flow is used. The multi-criterion optimization problem for finding optimal strategy of control is considered. The quality functionals of the optimization problem are represented through the stationary probabilities.

The research is devoted to the adaptation of theoretical and applied organizational grounds of favorable investment climate based on the establishment of an efficient mechanism of investment capacity increase in Ukraine. The main aim of the paper is to substantiate the mechanism of forming a favorable investment climate as the basis of investment capacity increase in Ukraine. The paper verifies the authors’ hypothesis on the adequacy of the substantiation of the mechanism of favorable investment climate forming as the basis of investment capacity increase leading to the substantial improvement of Ukrainian positions in international rankings. The dependence of Ukraine’s investment climate on the formed mechanism of its development is confirmed, and the necessity of its improvement is emphasized. The paper proves that forming of the favorable investment climate as the main precondition of boosted development, reproduction, and efficient use of investment climate at all levels is one of the most important strategic tasks that Ukraine faces. Economic, institutional-legal, and organizational-administrative mechanisms and implementation tools directed at improvement of the investment climate in Ukraine and the creation of conditions for investment capacity growth and its efficient transformation into an investment product are systematized.

The paper aims to develop a model for measuring economic system management efficiency of the Black Sea region of Ukraine through the context of sustainable development. The model includes the rates of social and economic efficiency, productivity, and performance. The proposed approach calculates the region’s economic system management efficiency. The respective evaluation criteria are systematized: economic and social efficiency of the region’s economic activity, productivity of the use of resources, and performance of the management system. The system of evaluation indicators by each criterion and mathematical apparatus to calculate them are suggested. The paper suggests methodical approaches to evaluate the economic system management efficiency in the region under transformation. They help determine the current level against similar indicators achieved within the country and the tendencies influenced by regional factors, form the “economic system management profile”, and identify the strengths and bottlenecks.

The article simulates the impact of the digital technologies’ development on economic growth, which makes it possible to find ways to improve the quality of various spheres of life and identify areas of the economy, the accelerated digitalization of which will ensure an increase in gross domestic product (GDP). The research used groupings of economic activities that directly influence the development of the digital economy. Using the data of regression models, the coefficients of GDP elasticity from the development of the studied sectors were calculated and used to forecast GDP under the development influence of the studied sectors while maintaining the existing trends. The dynamics of the e-commerce market development in Ukraine, the dynamics of production volumes of products (services) of the main types of economic activities in the field of digital transformation of the economy in Ukraine, the dynamics of financial results of enterprises in the information and telecommunications sector in Ukraine, the dynamics of capital investments in the field of information and communications of Ukraine, the dynamics of foreign investment in the development of the type of economic activity “information and telecommunications” in Ukraine, the dynamics of the development of the main areas of digitalization of the Ukrainian economy in 2010-2018 and the dynamics of GDP in actual prices were revealed. A correlation and regression analysis of the impact of the main indicators of the digital technologies sectors development on Ukraine's GDP is also carried out. The forecast extrapolation trend of production growth volumes of products and services in the information sector of Ukraine was built. A forecast of GDP growth in Ukraine has been constructed, taking into account the processes of digitalization of the economy in accordance with certain trends. The forecast dynamics of changes in GDP under the influence of the IT sector development until 2023 was also illustrated. It was found that Ukraine lags significantly behind most developed countries in terms of the level of industrial production development of information and communication technologies and equipment, Ukraine is completely import-dependent in this area. It has been proved that stimulating the development of information and communication technologies has significant prospects for activating digitalization processes in all spheres of the economy and society and increasing GDP.