How to Calculate an Average Percent Change

When you calculate an average percent change, you're objective is to find the change from one period to another.

Difficulty: Moderate

Instructions

Things You'll Need:

• Pencil or Pen
• Paper
• Calculator

Instructions

1. Know the basic formula. PR= (((Vpresent - Vpast) / Vpast) x 100) / N

2. Understand the symbols.
   
   PR= Percent Rate
   Vpresent = Present or Future Value
   Vpast = Past or Present Value
   N= Number of year

3. Learn the formula in words. Percent Rate equals Present (or future) Value subtracted by the Past (or present) value which is all multiplied by 100. All of this is then divided by the Number of Years.

4. Look at an example. In 1999, the population in My Town was 250,000. This grew to 280,000 in 2009. What is the average percent change for My Town?

5. Work the example out.
   
   Vpresent= 280,000
   Vpast= 250,000
   N= 10 Years
   
   PR= (((280,000 - 250,000) / 250,000) x 100) / 10
   
   PR= ((30,000/250,000) x 100) / 10
   
   PR = 12/10
   
   PR= 1.2%
   
   The population of My Town grew 12 percent between 1999 and 2009.

References

• Calculating Growth Rates

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