Ethomaz's Dismantling the Myths: Amazon.com's Best Sellers is Not Accurate to the Predict Overall Hardware Sales in US (Checking: Accuracy with Software)

[Soleron]

So it only got 4/5 months right. November was wrong.

Let's say it got December wrong too. You'd say you could exclude that because "holidays".
Or let's say it got January wrong. You'd say you could exclude that because it's "right after holidays"

4 data points after you've excluded 1 for an arbitrary reason is not good data and doesn't show reliability.