  This work is devoted to modelling and identification of the dynamics of the
inter-sectoral balance of a macroeconomic system. An approach to the problem of
specification and identification of a weakly formalized dynamical system is
developed. A matching procedure for parameters of a linear stationary Cauchy
problem with a decomposition of its upshot trend and a periodic component, is
proposed. Moreover, an approach for detection of significant harmonic waves,
which are inherent to real macroeconomic dynamical systems, is developed.
