How to revise my forecasting equation to improve the precision of forecasting

[Mirisage]

Hi Collegues,

I have the attached data set.

Table 1 Column D calculates the roll rate of outstanding balance from delinquency cycle_1 to cycle_1.

Table 1 Cell c28 shows the moving sum equation I have used to forecast the value of that cell based on previous 24 months actual data.

Column N of Table 2 applies the same forecasting equation for a known data range and column P calculates how well our prediction equation does the forecasting.

Sad to say that the % absolute deviation is way too unacceptable.

Could any one help me to improve this equation to increase the forecasting precision.

Thanks

Mirisage

[Craig_Houston]

I have not completely reviewed your approach, but the first thing that jumps off the page at me is what appears to be a seasonal pattern that your method is not accounting for... look at June of each year for example.  There is a significant drop off in roll rate each year at that time.

I see this post is over two years old.. I am sure you have figured this out by now.

[Mirisage]

Hi Craig,

Thank you for your contribution no problem even if the posting is old.

Regards

Mirisage