Let's say I have my data broken down by month and by categories A, B, and C. I have the historical data, but want to also show future months that build on each other according to a table like this:
Where those percentages are the prior applied to the prior month in estimating the value for each category's future months. For example:
Let's pretend the latest month values for A = 100, B = 200, and C = 300. The next month in the future, we would show A = 99, B = 196, C = 285. The month after that, we would show (with rounding to nearest whole): A = 98, B = 192, C = 271.
How could I go about doing this where I would maintain a table with the percentage adjustments and be able to forecast the next 12 months based on whatever the latest month of data shows?