The work is devoted to solving the scientific problem of development of theoretical and methodological principles and methodological tools to ensure the stability of the banking system in terms of changing the concept of financial market development, taking into account the permanence of volatility and turbulence. The banking system, being the main intermediary in the financial market of Ukraine, is at the center of the transfer of financial resources between all economic agents. At the same time, the financial market becomes a source of turbulent processes that can have a negative impact on the economy and provoke a crisis. Therefore, an important task is to ensure the stability of the banking system, especially taking into account the intensive development of modern financial technologies, the emergence of new financial instruments that force to reconsider the functioning concept of the modern financial market.
The content analysis of the main tokens – "stability", "volatility", "turbulence" – that characterize the state of the banking system and the financial market, allowed us to say that the token "volatility" is identified with the token "instability"; and the tokens "volatility" and "turbulence" have significant semantic differences. Such types of volatility as stochastic, implicit and explicit volatility, conscious and unpredictable volatility, flow volatility are distinguished by the author. The systematization of the existing approaches to the modern understanding of the token "financial market", as well as taking into account the influence of modern financial technologies are the basis of the author's definition.
The genesis of the digital economy, Fintech, as well as the formation of permanent volatility and turbulent processes in the financial market provoke transformations in the banking system of Ukraine, which is manifested in changing business models of banks, including neo-banks. They are classified as follows: digital banking, open banking, open X-banking with the transformation into a financial universal technology company.
The changes taking place in the financial market lead to a change in the paradigm of its further functioning and gradual transformation into a financial ecosystem, which appears as a set of service providers, infrastructure institutions, regulatory and supervisory bodies, which collaborate with the principles of sustainable development for the provision of integrated services with a focus on the individual profile of consumers – economic agents.
The application of a system of methods (correlation analysis; Sharpe's model to establish systematic and specific risk and determine the ß-coefficient; stationarity tests of Phillips–Perron and extended test of Dickey–Fuller; Granger causality tests; cointegration method, inverse reliability analysis method) allowed grounding long-term unilateral dependence of the development of the Ukrainian stock market on the world markets of Great Britain, Germany, the USA, as well as the local market of Poland.
The effect of overflow between the stock and bond markets was established the work with the use of cointegration tests and the influence of the American stock market on the domestic one was proved and its manifestation with a delay of one week, which will increase the strategy efficiency and tactics of bank securities portfolio.
A pair wise analysis of the relationship between the dollar / UAH exchange rate and index of «First Stock Trade System», between the exchange rate and prices of underlying financial assets (oil prices), as well as between the index of «First Stock Trade System» and oil prices showed in all cases a lack of long-term equilibrium and significant dominance of specific (diversified) financial risk that is formed within the domestic financial market.
The application of Mamdani's fuzzy logic model allowed to determine the integral indicator of internal and external stability of the banking system of Ukraine. As a result of the calculations it was found that the behaviour of the integrated indicator of the internal stability of the banking system is the most balanced, the behaviour of other indicators can be defined as unbalanced with a high level of volatility.
