Percentage Increase for 36 months of prices

Hi All

I am new to this and am hoping for anyones help with the following problem !

I have 36 months of prices for all of the food products my company buys, and need to get the percentage increase.

I can do this by taking the first figure and last figure and getting the percentage increase between the start figure and end figure.

What i want to know is; is there anyway of getting an average percentage increase across the full range of the prices.

I presume its going to include getting an average some how but after that i am stuck really.

Thanks in advance

Rhys J

Thanks SHG

Thats what i thought of doing, I think im just trying to over complicate it by taking into account the whole 36 months.

Thanks again !!!

Rhys