Who Will Top The Fortune 500?

By Geoffrey Colvin

In a business world so turbulent it feels like one long spin on the Humunga Cowabunga at the water park, an important fact has remained virtually unchanged for decades: who's biggest. Not which company is this quarter's most valuable or most profitable, but who's biggest, the one with more good-old-fashioned sales than any other. Nice to know some things never change, isn't it? Well, it's all about to change.

The most famous thing we do at FORTUNE is publish the definitive list of America's largest companies, the FORTUNE 500. And since the directory's beginning in 1955, the No. 1 company has almost always been the same: General Motors. Sure, a couple of times in the late 1970s and early '80s, Exxon floated to the top when oil prices spiked. Oil and Exxon receded; GM motored on. America's biggest is also the world's biggest: GM leads our Global 500 too.

Despite GM's amazing record, we can be quite confident that the company will not lead the FORTUNE 500 we publish next April. Barring calamity or another jump in oil prices, the new champ will be Wal-Mart, already the world's largest retailer by a mile. Like some cyborg athlete, Wal-Mart moves at a pace that would kill most of its competitors and somehow keeps it up while growing bulkier.

Now let's think really big. In the next 10 or 20 years, what company could become so mammoth we'd look back and chuckle at the notion that we actually once considered GM or Wal-Mart a sizable outfit? It's possible to imagine a few candidates--but you have to crank your imagination surprisingly hard. Here's why: as the world's largest company, Wal-Mart this fiscal year will take inclose to $200 billion in revenue. Think for a minute about how much money that is. If you sold something expensive, like cars averaging $20,000, you'd have to sell 10 million a year every year to reach it. If you could somehow sell something to every man, woman and child on earth, that something would have to cost $33, which is more than many of them could afford. And they'd have to buy it again every year.

Surely tomorrow's giants will come from the sectors that are revolutionizing business, no? They well may. But remember the stupendous scale we're talking about: combining IBM, Microsoft, Intel and Cisco, for example, wouldn't even come close to hitting our $200 billion mark. That fact points up a hard truth about corporate size. Infotech--or telecommunications or entertainment--may well be the world's largest industry in coming decades, but that doesn't mean it will harbor the world's largest company.

The greatest wild card, the sector with the vastest potential and murkiest future, is biotech. Developments that will cure cancer and extend human life beyond age 150 will arrive in this century. If one enterprise were to commercialize these developments in some proprietary way, then it's easy to imagine that firm's becoming the world's largest by far. But these are matters of life and death, so it's just as easy to imagine political pressures preventing biotech from spawning the globe's biggest company.

I hate to sound unimaginative, but you know who's easy to picture as the world's largest business 10 years from now, maybe even 20? Wal-Mart. It's been growing around 20% a year, and while extrapolation is always hazardous, if you're at $200 billion a year, growing 20% annually--or even 10%--you are extremely hard to catch. Wal-Mart is expanding aggressively around the world, as it must. Most important, it owns by far the most advanced back-end infotech system--for managing inventory, logistics, working capital, customer data--in retailing. Most people wouldn't suspect it, but Wal-Mart is one of the world's most advanced e-companies.

Business will only get more insanely turbulent. But after this year, we won't be worrying about who's biggest for a while.

Geoffrey Colvin is editorial director of FORTUNE