Broadband and internet enterprise analyst Om Malik notes a distinct, multiyear pattern in Apple's stock movement leading up to the annual Macworld convention, and through earnings the following week:
From third week of December, and ride it right to the eve of Macworld, there is a good chance there will be a 10% (or higher) appreciation in the stock. Call it the Macworld madness. It's traded down after that, typically, especially after the earnings get announced. Take 2005 as an example. Stock gained 10.41% right up to Macworld, when Steve Jobs introduced Mac Mini. Then, slip sliding away once the earnings were released. (2003-2004 performance was actually better!)
The sentiment for 2006 was actually better, even though the products announced at Macworld were kinda expected and lukewarm. The iPod powered Apple in 2005. The stock gained 12.13% in from the third-week-of-December to Macworld time frame. The earnings, today, resulted in a southward turn in the stock.
It would be interesting to look at data from before 2003 to see if the pattern has a longer-term basis.