The base period of an index is the benchmark time period in the index. In Index Builder, the value(s) in the base period are set to 100.
You can set up:
A fixed base period of the same frequency as input series
A floating base period by using the first period available
A fixed base period of lower frequency than input series
Examples of specifying base period
Example 1. Setting the base period frequency same as frequency of inputs
If the inputs are in monthly frequency, when you specify base period = 2010M1 and base period frequency = monthly, then the value of index will be fixed to 100 for January 2010.
Example 2. Setting the base period frequency lower than frequency of inputs
If the inputs are in monthly frequency, when you specify base period = 2010 and base period frequency = annual, then the value of index will be fixed to an average of 100 for the months in 2010.