One question that comes up all the time in our work is what is the difference between a percentage change and a rate of increase?  Answer:  They are the same idea, just expressed differently.  For instance, if you say the price of oil increased  by 100% that is the same as saying that the price of oil doubled.

So mathematically, the 100% increase is equal to a 2.0 times increase.  So generally, you can subtract one from a change factor (i.e. 2.0 times higher) to get the percentage increase.