This got me thinking though about the golden question about customers... "Why do customers do what they do?". Like the age old question about "life and everything", this one also does not have a clear and finite answer. You can pick up a number or a reason from the air, so to speak, and try to explain customer situations to those numbers. I say "try", because they will not always be explainable... many times you will attribute them as "outliers" or "special conditions".
Bottom line is that, the customer psychology is a very complex being and not something you can define in terms of mathematics or logic. There is a lot of emotion attached to any action that a customer takes.