The study introduces a concept of composite indicator based on data concerning the activity of main sectors of the national economy in monthly intervals. The indicator has been created for further studies in business barometers for the Poland's economy. The introduced concept of this general business indicator is based on quantitative data, parallely, within a framework of the same research project, studies are conducted; how to base the composite indicator on qualitative data. Three alternative formulas of the indicator, based on the quantitative data (marked in the study with symbols GC11, GC12, GC15) were computed for the period 1975 - 1995 and tested with the X11-ARIMA and PAT procedures, used for economic fluctuations in the OECD countries. The final part of the study contains a findings analysis, concerning disintegration of series into four components: irregular, seasonal, cyclical and trend, including a chronology of economic fluctuations and characteristics of amplitudes. To make exposition clear, it was preceded by a brief presentation of the analysis' instruments and definitions of the used notions and categories. In this part of the study a comparison could be made between suggested composite indicators and GNP indicator, demonstrated in monthly intervals in the independent pioneer studies by I. Kudrycka and R. Nilsson in business barometers for the Polish economy, conducted since 1993 with analogous computational procedures, but based on a different data set.