



 
Hi Anna, I would calculate the difference as the new value minus the old value. If this difference is positive there has been an increase and if it is negative there has been a decrease. You then want to state this change as a percentage but the question is a percentage of what? Not everyone does the same thing. I think you should report the percentage change as a percentage of the old value so the expression would be
What is important is how you state the result so it is clear what you did. Suppose the 2005 value was 400 and the 2005 value was 500 then I would calculate
and say "In 2006 we had an increase of 25% of the 2005 value". Suppose the 2006 value was 500 and the 2007 value was 300 then I would calculate
and say "In 2007 we had an decrease of 40% of the 2006 value". I hope this helps,  


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