Figuring Inflation

The most common form of figuring inflation uses the consumer price index (CPI) to monitor the changes over time. These numbers are tracked and compiled, by region, by the Bureau of Labor Statistics. There are different indices but the most revealing of all is the CPI for all items. This includes energy, food, service, and other costs. The only notable thing it excludes is healthcare costs. These numbers give us an idea of what consumer spending is for many different items and categories over a period of time, which gives a fairly accurate depiction of inflation itself.

To figure inflation the first thing we will need is a data set for the regions you are interested in. I chose national and southeast. Keep in mind that it takes a while to compile all the data, so there is always a lag in what is available. Here are the numbers since 12/2006:

National CPI Southeast CPI
12/2006 201.800 194.800
01/2007 202.416 195.021
02/2007 203.499 195.950
03/2007 205.352 197.904
04/2007 206.686 199.618
05/2007 207.949 200.804
06/2007 208.352 201.675
07/2007 208.299 201.571
08/2007 207.917 201.041
09/2007 208.490 201.697
10/2007 208.936 202.155
11/2007 210.177 203.437
12/2007 210.036 203.457
01/2008 211.080 204.510
02/2008 211.693 205.060
03/2008 213.528 206.676
04/2008 214.823 208.085

 We can then use this formula to calculate the change over time as a percentage, which is inflation:

 % inflation for period = [ (cpi2 – cpi1) / cpi1 ] * 100

To calculate the total inflation throughout 2007 we take the index from December 2006, to account for the change in January 2007, and the index from December 2007 and plug them into our formula:

[ ( 210.036 – 201.800 ) / 201.800 ] * 100 = 4.08%

Likewise, we can calculate the inflation for 2008 using the same methods, which show us to be off to a rocky start:

[ ( 214.823 – 210.036 ) / 210.036 ] * 100 = 2.28%

These calculations are important to keep in mind when it comes to negotiating salary, regardless of whether it is for a job offer, a raise, or anything else. If the inflation rate you calculate is less than when the compensation increase is, you are losing real income, if the inflation rate is the same then you are breaking even, and if the inflation rate is lower then you are increasing your compensation.


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Jason McDonald

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