How to fill in the chainladders with the data of the inventory, sales and purchase (part one)

Previously I did a lot the chainladders filled up with the claim data of the insurance business to look into the development and the trend of the incurred claims. Not only I had to find and gather the claim data for those chainladders, but I also did the interpretation and projected the trend of the upcoming incurred claims on the quarterly basis.
At that time the regional team header used to tell me that the other significant business data could also be analyzed through those chainladders. To extend this idea, I have determined the data of the inventory, sales and purchase for the chainladders to give us more business information. See below the example.

Given that the purchase results from the current inventory less the beginning inventory plus sales, we can build the development and the trend of these three items from the actual data at each end of the time from the past to the present and the estimate projected data for the future. The process is shown below.

How to fill in the chainladders with the actual data of the inventory, sales and purchase according to the demonstrated pictures
1. Create the chainladders of the inventory, sales and purchase as at each end of the transact month rolling backward from the current month which is the last row of each chainladder.
2. Relating with the item one, each row of the chainladder starts differently its own transact month under the header of the development month numbered one. For example; at present, the current month is Mar so the last row is Mar under the development month numbered one while the rolling month of Feb starts its transact month of Feb under the header of the development month numbered one.
3. Following the item two, each column with the header of the development month rolls forward from the development month numbered one to the current month of Mar of which the number upwards runs from the number one to twelve rather than the name of month. By the way, each row will end its data at the column of the current month of Mar which is represented with the ordering number of the development month.
4. Prepare the actual data of the inventory, sales and purchase for the chainladders of inventory, incremental sales and incremental purchase after processing from item one to item three above.
5. The cumulative sales and purchase chainladders are accumulation of the item four
6. All development factors are from comparing the data year on year within the cumulative chainladders.
7. Weigh the factors derived from item six and then select the suitable factors for the future trend (the area of the new input of the future ratio) to calculate the projected numbers. (Regarding the factors, we can adjust them based on the new information we have just got or the rapid change in goods.)
8. Create the executive summary to display all we have had: the actual data and the estimate projected data. (Two kind of summaries: one from projected purchase and another one from projected sales.)
9. As for item8, the data of sales and purchase are the total accumulating amount in the row of each transact month of the chainladders while the current inventory is the balance from each row as at the end of the current development month.(The total accumulating purchase - the total accumulating sales = the current inventory balance)

After we have had the data of the inventory, sales and purchase in the chainladders, we can use this useful business information to change or improve our business handling and move towards our best success.

The data in the pictures is only manipulated for calculating the inventory projection. However, you can fill in the chainladders with your own data from the business and you will see the business information that can tell you something.

The following link is the excel file for trying. And it might call update but you must not update it.
http://sdrv.ms/16FEnHD