From Quartz:

 

When Tim Cook took control of Apple, he seemed to have a clear mission: manage the company’s difficult transformationfrom a high-growth stock market story to a more staid, but still incredibly profitable, dividend-paying blue-chip. But no one saw this year coming. Apple shares have surged more than 40% so far this year, creating more than $160 billion in market value for shareholders. (By way of comparison, that’s roughly the market valuation of the company once regarded as its greatest rival: IBM.)

 

What’s driving the growth expectations? Obviously, the wild success of the latest incarnation of the iPhone, and growing expectations for a massive Christmas season. If Cook had merely been a successful steward of Steve Jobs’ legacy, he would have gone down in management history. But if Apple shares are any indication, shareholders think he could do much more.