Interpolate monthly growth from known Annual Growth

[nopointing]

Cross post here: http://www.mrexcel.com/forum/excel-q...al-growth.html

Hi All,

I have a series of values

Jan-11 101
Feb-11 111
Mar-11 118
Apr-11 135
May-11 140
Jun-11 149
Jul-11 151
Aug-11 161
Sep-11 166
Oct-11 175
Nov-11 187
Dec-11 191

So total 2011 = 1785
I also know that 2012 grew by 71% so there fore 2012 = 3052.35

Now, I'd like to extrapolate 2012 monthly data to get a steady growth for 2012 which will add up to 3052.35

So for Jan'12 it would be Dec'11*(1+X%) and then Feb'12 would be Jan'12*(1+X%)

My question is what is this X%? I've interpolated the 71% growth to monthly as 4.57% but if I use that as my X I get 2012 = 3101.563 which is actually 2011*(1+74%) instead of 71% as I know the total to be for 2012.

Any ideas how to find the correct X to show upward growth?

Thanks very much for your help

EDIT: Adding crosspost - apologies for not doing before

[FDibbins]

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[joeu2004]

See responses in the crossposting at http://www.mrexcel.com/forum/excel-questions/784571-interpolate-monthly-growth-known-annual-growth.html