The base year is described as the starting point from which we measure changes in:

1. The base year anchors the index. 2. Economists arbitrarily choose one year to be the base year. 3. It is the starting point from which we measure changes in prices. 4. The index is set to a round number in that year. _Source: OpenStax Principles of Macroeconomics for AP Courses 2e (CC BY 4.0), Ch 8 'Inflation'_