Wii U sales trend may be just as expected if we look at Nintendo's home console sales.

[Super_Boom]

Six data points is not enough to quantify a trend, and certainly not enough to establish one of those six points as an outlier. Especially when said points are spaced at near five year intervals.

I work as a Manufacturing Engineer, and spend a good deal of time analyzing in-process data in order to assess trends and potential modes of product failure over time. If I ever went to our Quality Engineering team with the limited data I see in the OP, you can believe I'd have a hard time being taken seriously.