Video games often follow a predictable model of sales. Several factors must be taken into place before making any such model.
In the United States, NPD December accounts for nearly 25%, while October, November, and December account for 50% of the calendar year's revenue. Additionally, history shows that from January to October within any given year the data for a system's installed base is roughly a linear function. This is always subject to change if there is a price cut or a system seller game like Halo.[1]