I have a lot of quarterly data for market size. I am trying to find out how
I can calculate the average growth rate for this market. For example, if I
know

- $10m was the initial market size
- $100m was the final market size
- it took six quarters to grow from $10m to $100m

Then what was the growth rate? I am feeling very silly because I used to be
able to work this out years ago but I've forgotten the formula and I couldn't
find what I wanted in Excel help.