Improving of the methodological tools for the national economies behavior’s forecasting in the context of increasing the validity and analytical characteristics of state economic strategies in conditions of high volatility, lack of trend stability and non-stationary dynamics of external and internal socio-economic processes by implementing interdisciplinary methods of Fourier analysis and their adaptation to the specifics of the socio-economic systems’ functioning and development. Methodology. The forecasting’s targeting as an important independent stage in the process of analytical assessment of the balance of development is performed on the basis of structuring, division into stages, systematization, and grouping. Justification of the interdisciplinary approach for forecasting of national economic system’s development is carried out by methods of analysis and synthesis, comparison and practical testing. Establishment of the economic dynamics’ structural regularities and forecasting of a trajectory of national economy development are executed by harmonic and spectral analysis of the dynamic systems’ fluctuating processes. The results. The paper’s attention is focused on the specific features of macroeconomic dynamics’ time series as a basis for the forecasting of national economies development, namely their short duration, non-stationary, aperiodic, polyharmonic and their impact on the formation of adequate methodological support for forecasting. The possibility and efficiency of spectral and harmonic methods using for analysis oscillating processes of national economic system’s development are substantiated. A harmonic model of Ukraine's economic development’s trajectory during 1991-2020 is formed, which allowed to analyze the fluctuating component of the macroeconomic indicators’ dynamics on the basis of actual data that included all the initial information contained in the time series. By distinguishing economic cycles, their amplitude-frequency characteristics, the current phase of Ukrainian economy’s development is characterized. On the basis of the economic dynamics’ model, being used the indicator of annual GDP growth, forecasting is executed and short-term, average-term and long-term tendencies Ukraine’s economy’s development are established. Scientific novelty. The extending of theoretical and methodological tools for forecasting of main trends in national economies, based on harmonic and spectral analysis, is allowed to form a structural approach to the analysis of economic dynamics in the context of selection of its decisive harmonics and basing on their characteristics to make conclusions about the current level and projected national economic systems’ development. Practical significance. The adapted and regulated procedure of harmonic and spectral analysis of socio-economic systems’ oscillating processes became the basis for forecasting the level, rates and proportions of national economic systems development.
From Convergence to Divergence: Portuguese Economic Growth, 1527–1850
