Apple stock is stumbling ahead of the expected announcement of the iPad Mini.
The slide, which began in mid-September, bucks the usual trend of share prices climbing on rumors of a new Apple product launch.
The smaller-sized, lower-cost iPad is expected to be unveiled next week, with press-conference invitations supposed to go out Wednesday.
When markets closed on Tuesday, stock prices had fallen .36 percent to $635.85.
There are several theories to explain the latest dip.
Last month, Apple released its redesigned iPhone 5, easily its most lucrative enterprise, skyrocketing its stock. But while early sales were high, CNET noted the company is facing unprecedented competition in the smartphone market as Android's market share increases.
Also read: iPhone 5 Presales Sell Out in About an Hour
Moreover, riots and protests at the Chinese Foxconn factories where the iPhone 5 is built have dented Apple's tightly controlled corporate image.
And, last month, Apple CEO Tim Cook (pictured above) apologized to customers frustrated with huge errors in Apple's much-hyped new Maps service that foregoes Google Maps data.
Also, the recent one-year anniversary of visionary CEO Steve Jobs' death may have reminded stockholders of seemingly better times.
Another theory, reported widely since 2009, suggests that hedge-fund managers and investors purposely hammer down Apple's stock ahead of big product launches so they can profit off a "slingshot effect," where stock price plummets then shoots up rapidly in a short time.
Updated at 2:10 p.m. PST with the closing stock price.