SEATTLE - FIVE and a half months ago, word that Steve Jobs would only work part-time as he recovered from a liver transplant would have sent investors into a selling frenzy, so closely linked was Apple's charismatic co-founder and CEO to the company's success.

Wall Street has grappled with the implications of Mr Jobs' illness since August 2004, when investors learned the CEO had kept a cancer diagnosis secret until after he underwent surgery.

Investors feared a half-year absence would leave one of the oldest computer makers adrift, because Mr Jobs had become the essence of the company he started in 1976. But in the last few months, the company released must-have gadgets and software improvements with nary a public hiccup.

Its shares have almost doubled, raising the question of how central Mr Jobs is to Apple today? The company's past silence on matters of Mr Jobs' health made shareholders jittery when Mr Jobs appeared increasingly, even alarmingly, thin last year. Easily spooked, investors sent the stock tumbling 5 per cent to its lowest point in a year on a rumour last October that Mr Jobs had suffered a heart attack.

Then shares slipped 2 per cent in December when Apple said that Mr Jobs would not speak as usual the next month at the annual Macworld conference, then bounced up 4 per cent on Jan 5 when Jobs explained his weight loss as a treatable hormone imbalance.

They sank 7 per cent a week later after Apple said he would be taking six months off because his medical problems were more complex than he initially thought.

It is not yet clear how investors will take the latest word, that Mr Jobs had a liver transplant two months ago in Tennessee, according to The Wall Street Journal, and that he will likely work part-time, at least at first.

Apple has not confirmed the report, and has said only that Mr Jobs is looking forward to returning to Apple at the end of the month. -- AP