Base Date

Base Date

The date against which the performance of an index is measured. For example, suppose the base date is January 1, 2001, and the initial value of an index is 100. If the index is 150 on April 16, 2009, it means that the value of the index is 50% higher in 2009 than it was on New Year's Day in 2001. It is also called the reference date. See also: Base Value.