I am currently working on a project where i need to predict next 4 quarters customer count for a retail client based on previous customer count of last three years i.e. quarterly data means total 12 data points. please suggest a beat approach to predict customer count for next 4 quarters.
Note:-I can't share the data but Customer count has a declining trend YOY.
Please let me know if more information is required or question is not clear.
With only 12 data points you would be hard-pushed to justify anything more than a simple regression analysis.
If the declining trend was so strong that you were at risk of passing below 0 sales you could look at taking a log to linearise the data.
If there is a strong seasonal cycle you will need to factor that in, but doing so also reduces the effective sample size from 12 to 9 quarters of data (three degrees of freedom being used up by the seasonalisation).
Thats about it really.