TimeValueOfMoney11

The Consumer Price Index (CPI) shows how inflation
has increased the cost of a typical family’s purchases.

Economists track the general level of prices using several different price indexes.
The best known of these is the Consumer Price Index, or CPI.
This measures the number of dollars that it takes to buy a specified basket
of goods and services that is supposed to represent the typical family’s purchases.
Thus the percentage increase in the CPI from one year to the next measures the
rate of inflation.