EN
The general indicator of business activity for Poland (GCI), developed by Z. Matkowski, and its component parts reflecting the production activity of five major sectors of economy (industry, construction, agriculture, transport and trade), filled with monthly data covering the period of 1975-1997, have been subject to spectral analysis in order to identify periodic fluctuations. The analysis included various kinds of data (raw data, seasonal components, trend-cycle, trend deviations, and data transformed by Fourier analysis). Unit root tests were applied to distinguish between trend stationary and difference stationary time series. Apart from the seasonal oscillations, the GCI time series reveal business cycles ranging between 7 and 11.5 years (average 9.5 years). These cycles are well reflected by the dynamics of industry and transport. Construction and agriculture seem to reveal even longer cycles while the retail trade reveals a shorter trade cycle. These findings are largely in line with the results of a parallel examination of the growth cycles seen in the deseasonalized, detrended and MCD-smoothed time series. However, due to a relatively short period covered by the analysis and the change in economic system, these findings may not hołd in the future.