Price index

A price index is a number used to measure how expensive something is over time. It's like a special kind of average. For example, let's say someone wants to calculate the average price of apples in the United States. They would find the price for apples in different places around the country, and then calculate the average. The price index does the same thing, but instead of finding the average price of apples, it finds an index number that changes over time. This number is used to tell us how much more or less expensive something is compared to when it was first measured. The index number can help us figure out if prices are going up or down.