A sequence of observations showing the formation of studied phenomenon in subsequent periods (days, months, quarters, years, etc.).

In the time series can be extracted several components resulting from the impact of various factors on a given phenomenon. The following components of the time series are distinguished:
1) Development trend;
2) Cyclic fluctuations;
3) Seasonal fluctuations;
4) The rest part.

• Statistical series

• Typological grouping
• Variant grouping
• Development trend
• Cyclical fluctuations