Index Numbers

Useful for making comparisons among a series of numbers.
Creating an index involves three steps:

    1. Select the year against which you want to make comparisons (i.e., the base year)
    2. Divide the base year by 100 (or just move the decimal point two spaces to the left)
        (e.g., for year 2004: 3474/100 = 34.74)
    3. Divide all other numbers by the base (e.g., for year 2009: 4223/3474 = 1.2156) and
        then multiply by 100 to get an index of 122 for year 2009 (always express the index
        number as a whole number)

Remember: the base year index value = 100 and it is against the base year that all
                  comparisons are made.

                                                                                                   



                                                                                                 How to Read                                                                  

                                                                      In 2000, advertising spending was 39 percent lower than 2004;
                                                                      Spending in 2007 was 48 percent higher than 2004.