UPDATE: Apple stock was down about 2.5 percent in midday trading.
When the CEO of the world's second most valuable company takes a medical leave of absence, the public wants answers.
Two questions loom: How serious is Steve Jobs' medical condition? Will Apple still be Apple without him? While certainty is nearly impossible, speculation about Jobs will likely drive the direction of its stock.
Investors will look to the past. In 2004, Jobs announced he had pancreatic cancer and subsequently underwent surgery. In 2009, Jobs took a medical leave of absence for nearly six months, during which time he received a liver transplant. Apple shares were down about 7 percent after hours on the day of Jobs' announcement in January 2009, but they rose fairly steadily for the remainder of the year.
Apple's rise continued. The company's value surpassed Microsoft's in May of last year, and it's now second only to ExxonMobil's.
If its stock drops, some analysts, including Morgan Stanley's Katy Huberty, say that would be a major buying opportunity. Apple is set to report earnings on Tuesday, and estimates are high. Under normal conditions, that would likely boost the stock price.
Others are concerned about what the secrecy surrounding Jobs' absence means for the company. Ben Heineman, former general counsel for GE, writes:
The right to privacy of a CEO about medical conditions should be outweighed by the need for disclosure under certain conditions, including the following: when there is a life-threatening illness; when there is a substantial leave of absence that raises questions about current and future ability to lead the company; or when an illness impairs a CEO's ability to do his or her job.
It seems clear that one these conditions applies here.
If Apple's share price falls, the Nasdaq, which has enjoyed a dramatic rise in recent months, could take a hit.