Algebraically this works, but I'm looking to understand (1) why it works and (2) if there is a simpler formula.
Problem: I want to get total % change over time.
Example Data -
Jan 2013 - 14.29%
May 2013 - 25%
Oct 2013 - 20%
**Solution Methodology:** 1. Take a random baseline number to plugin: 100 2. Calculate the actual numbers: Jan 2013 - 14.29% Increase = 114.29 May 2013 - 25% Increase = 142.8625 Oct 2013 - 20% Increase = 171.435 3. Calculate Total % Difference: (171.435 - 100) / 100 = 71.435% 4. Plug in variables to determine formula to do this: Baseline Number = X A = Jan 2013 Increase % = (x)(A + 1) = (xA + x) B = May 2013 Increase % = (xA + x)(B + 1) = (xAB + xA + xB + x) C = Oct 2013 Increase % = (xAB + xA + xB + x)(C + 1) = (xABC + xAC + xBC + xC + xAB + xA + xB + x) = x(ABC + AC + BC + C + AB + A + B + 1) Calculate % Change = (x(ABC + AC + BC + C + AB + A + B + 1) - x) / x
Final Algebraic Formula = ABC + AC + BC + C + AB + A + B
Other Notes Interestingly enough if I only looked to get the Total % Difference of May 2013 and Jan 2013 the algebraic formula becomes: AB + A + B
There is a chance I'm overcomplicating this or am calling it the wrong thing.
Appreciate your help!