Properties of Time Series Data

Time series data has the following properties that needs to be considered:

1. Time series is always defined with respect to time (annually, monthly, etc.)
2. Autocorrelation is present most of the time.
3. There are always shocks present in time series.

If a time series is not following property number 3, then it is not a time series, however, autocorrelation may or may not be there, but it is present in most of the cases.