What Jobs is to Apple

Apple Inc. conveniently chose a US stock market holiday to tell the world its chief executive would take another health-related leave of absence. Still, the news yesterday sent Apple shares down more than 7 percent in trading in Frankfurt. Apple’s open on US markets this morning will be a bumpy ride.

Of course, all this matters to owners of Apple shares. But it also means something to many more investors because the Apple juggernaut has become so valuable and the company’s stock is a member of broad stock market indexes.

With a market value of about $320 billion, Apple is America’s second-most valuable stock and trails only Exxon Mobil Corp. by that measuring stick. Apple shares account for about 2.5 percent of the entire Standard & Poor’s 500 stock index alone.

The idea that Jobs, 55, might need a break for medical reasons is no great shock. His health and appearance have been intensely scrutinized ever since he underwent surgery related to pancreatic cancer in 2004. Jobs took his first leave that year. He took time off again in 2009 and underwent a liver transplant. In an e-mail to Apple employees yesterday, Jobs said only that he needed time now to “take care of my health.’’

No other company has grown so big and enjoyed success so directly linked to a single person as Apple and Jobs. In that sense, Jobs is a unique figure in American capitalism. So what does it mean for Apple if he isn’t there?

It’s not fair to many people who work at Apple, but Jobs is identified as the driving force behind all those elegant, game-changing new products and the company’s staggering stock market success. Jobs returned to the company he helped create as it was floundering in 1996. The first decade of the new century belonged to Apple shares like no other stock in the world. Along the way, the world got in line to buy millions of iMacs, iPods, iPhones, and iPads. He introduced them all.

An investment of $100 in the S&P 500 index a decade ago would leave you with $115 today, thanks to dividends. Another $100 investment in Apple shares at the same time would be worth about $4,336 now.

That kind of appreciation isn’t a big iBubble. Those wildly popular new and innovative products drove profits dramatically higher. Over the previous four fiscal years, Apple earnings have soared from $2 billion to $14 billion. The company was sitting on more than $50 billion of cash and investments on Sept. 30.

Along the way, Apple shares became a staple in the portfolios of mutual funds that own growth stocks. Will Danoff, manager of the $75 billion Contrafund, is the largest single fund owner of Apple stock. Danoff has invested 7 percent of the giant fund’s assets in those shares, by far his largest position.

Putnam Voyager, a local growth-stock fund that has enjoyed outsized returns over the past two years, earned some of those gains with a big investment in Apple. Manager Nick Thakore also counts Apple as his largest single holding, amounting to 5 percent of the fund’s assets.

Another temporary leave by Jobs shouldn’t be such a big deal for Apple or its stockholders. Tim Cook, the company’s able chief operating officer who stepped up during Jobs’s two previous leaves of absence, will be in charge again.

Apple’s track record during those previous leaves should also be reassuring. The company’s shares climbed 201 percent in 2004 and gained 147 percent in 2009. This year, Apple will get a big business boost when the iPhone becomes available to Verizon Wireless customers for the first time. We’ll find out how much momentum the Christmas season provided Apple when the company issues its quarterly financial report today.

But no chief executive runs a company forever, including Jobs. This is a good time to think about Apple’s future in that context. The company’s picture would be very different, and Apple would become a riskier investment proposition.

Apple’s business recipe is part technical marvel and part marketing wizardry. Steve Jobs is a great innovator on both counts, bigger than life as a business leader. You just don’t replace people like that.

Steven Syre is a Globe columnist. He can be reached at syre@globe.com.