This book includes discussions related to solutions of such tasks as:

• probabilistic description of the investment function;
• recovering the income function from GDP estimates;

• development of models for the economic cycles;
• selecting the time interval of pseudo-stationarity of cycles;
• estimating characteristics/parameters of cycle models;
• analysis of accuracy of model factors.

All of the above constitute the general principles of a theory explaining the phenomenon of economic cycles　and provide mathematical tools for their quantitative description. The introduced theory is applicable to macroeconomic analyses　as well as econometric estimations　of economic cycles.