Hi, im having trouble calcualting the growth factor in a set of data (column
a has the year and column b has the percentages) no matter what i do it
doesn't work PLEASE HELP!

Pleas give a sample of your data, with "before" and "after" results if
you know them. Also, please tell us what you have tried that doesn't
seem to work.

"Laura" wrote:
im having trouble calcualting the growth factor in a set of data
(column a has the year and column b has the percentages)
no matter what i do it doesn't work PLEASE HELP!

It is not clear whether you want to the total percentage growth
after N years or the average percentage growth over N years.

Also, it is unclear whether the "percentages" in column B are
the annual growth rates or "the set of data", which just happen
to be percentages. I ass-u-me column B is the annual growth
rate, for the most part.

However, it is also not clear whether or not you have any gaps
in the data -- that is, whether or not all years are represented.
And if not, whether the "percentage" (growth?) in column B
represents just the one year (not useful), or the total percentage
growth for all years between the previous row and the current
row, or the averge percentage growth for those years. I will
ass-u-me that you have no gaps in the data.

If you have periodic growth rates r1,...,rN, the total growth rate
is (1+r1)*...*(1+rN) - 1. In Excel-speak, you can use the following
array formula (ctrl-shift-Enter), assuming 6 periods:
=PRODUCT(1+B1:B6) - 1 .

The average growth rate is (1+totalGrowthRate)^(1/N) - 1. In
Excel, you can enter the following array formula (ctrl-shift-Enter):
=PRODUCT(1+B1:B6)^(1/COUNT(B1:B6)) - 1 .

Or if C6 contains the total growth rate, the following non-array
formula will work: =(1+C6)^(1/COUNT(B1:B6))-1 .

Of course, you can replace COUNT(B1:B6) with a constant, if
you prefer. I use it here primarily to indicate that it is the total
number of periodic data.