The value of the index in the base year is typically set to an arbitrary level of 100. This is done for simplicity and to provide a reference value for comparison in the measure of business activity or economic or financial index. The base year can be any year, but analysts typically choose recent years. It is periodically updated to keep data current in a particular index. For example, to find the rate of inflation between 2016 and 2021, 2016 is the base year or the first year in the time set, and the index value of the base year is conventionally set to equal 100. Similarly, when calculating real GDP in the US, the year 2012 is used as the base year. In summary, the value of the index in the base year is always set to 100 for simplicity and comparison purposes.