What is a dollar worth? The Consumer Price Index (CPI) is a measure of the average change in prices over time in a market basket of goods and services. The Bureau of Labor Statistics releases CPI data monthly.
Consumer Price Index and Inflation Rates, 1913- Consumer Price Index and Inflation Rates (Estimate), 1800- How the CPI is used to make these calculations

• Limited to years from 1913 to 2008.
• Data from consumer price indexes for all major expenditure class items.
• An estimate for 2008 is based on the change in the CPI from fourth quarter 2006 to fourth quarter 2007.
• Base year is chained; 1982-1984 = 100
• JavaScript-enabled browsers only.

How the CPI is used to make these calculations.

• What would an item or service purchased in 2008 be worth in 19?? dollars?
  
  Example:
  
  The CPI is used to calculate how prices have changed over the years. Let's say you have $7 in your pocket to purchase some goods and services today. How much money would you have needed in 1950 to buy the same amount of goods and services?
  
  The CPI for 1950 = 24.1
  The CPI for 2008 = 215.6
  Use the following formula to compute the calculation:
  1950 Price = 2008 Price x (1950 CPI / 2008 CPI)
  $0.78 = $7.00 x (24.1 /215.6)
  

• What would an item or service purchased in 19?? be worth in 2008 dollars?
  
  Example:
  
  Let's say your parents told you that in 1950 a movie cost 25 cents. How could you tell if movies have increased in price faster or slower than most goods and services? To convert that price into today's dollars, use the CPI.
  
  The CPI for 1950 = 24.1
  The CPI for 2008 = 215.6
  A movie in 1950 = $0.25
  Use the following formula to compute the calculation:
  2008 Price = 1950 Price x (2008 CPI / 1950 CPI)
  $2.24 = $0.25 x (215.6/24.1)

  A full-price movie at a Minneapolis theater costs between $6.00 and $9.00. Looks like movies have increased in price faster than most other goods and services.