I am using PROC GENMOD with time series data, I have tried to work with Negative Binomial, Poisson, GEE and Zero Inflated Poisson, but in each case when I score my validation dataset, I am getting predicted values which are never zero.
E.g. A customer might buy fuel every 4 weeks, the model does not predict the weeks in between fuel fills as zeros.
Is there a better way of predicting the weeks with zero fuel fills? I assumed Negative Binomial would be able to do this, but the lack of predicted zero outcomes, which represent 78% of the fuel filling weeks (by customer) has made this model ineffective.
Thanks in advance!!