The How And Why Behind This Year’s Fortune “40 Under 40” List

Tonight marks the celebration of Fortune magazine’s annual “40 Under 40” issue, which appeared on newsstands yesterday. In anticipation of the event, Leigh Gallagher, Fortune‘s assistant managing editor, gave us a little insight into what, exactly, goes into the making of such a list…

How did the team at Fortune decide who made the list?

It’s a really fun and exciting process because each year new people emerge — and obviously many people turn 40 and become ineligible, so the list has a natural churn. People always ask me what it “takes” to get on the list. It’s a combination of size, scope and relevance of the business a person runs; his or her power, influence and reputation both in his or her industry and beyond; and his or her potential as a future leader.

Was there any attempt to balance well-known names with lesser-known entrepreneurs and business people? Women with men?

We always want a list that’s reflective of the broader business landscape in general, but inevitably we end up with a heavy representation from the tech sector simply because that happens to be where a lot of young ambitious people have been heading in recent years. One of the most interesting aspects of this list is the sense of discovery it offers across all industries.

The issue of women on this list is a tough one. Every year we shake the trees really hard to make sure we’re not missing anyone obvious, but every year there are far fewer women than men. I’ve talked to a lot of people about why this might be the case. Much of it has to do with the fact that women who want to have families tend to leave the workforce temporarily precisely around the time they’d appear on this list. If you look at the list of powerful women in their 40s in business there are many more of them and Fortune highlighted many women in the business world during the Most Powerful Women Summit in DC earlier this month.

Big names in tech seem to dominate the top of the list. Was this intentional, or just a sign of the times?

It’s not intentional in the least. But when you look at what Sergey Brin and Larry Page have done it’s hard to put them anywhere except the top five. And few can argue with the power, size, scope and influence of Facebook right now. But if you look at someone like Raul Vazquez — he controls a third of Wal-mart’s $258 billion U.S business — he belongs right where he is on this list, at number four. I’d love for us to have a year in which the top five are brand new names. That would mean we’d have found the five best stories in business.

Why should Fortune readers pay close attention to this list? What does it have to tell us about the future of media?

This list is important for several reasons. One, it shows us that in the face of these incredibly challenged economic times, there are still amazing growth stories out there, and that the entrepreneurial and innovative spirit that drives business is still very much alive and thriving. Two, it identifies leaders of tomorrow. In only the second year of its current iteration, the list is too young for us to identify how many future big-company CEOs we’ve spotted, but it’s worth keeping tabs on these people. Third, it’s just really entertaining reading. But I’m biased.