As VC Aileen Lee pointed out in a much chattered about TechCrunch post earlier this year, building a company that reaches a billion-dollar valuation is rare, almost as rare as a unicorn sighting, in fact. Of the thousands upon thousands of fledgling businesses started in the U.S. each year since 2003, just 39 have achieved this holy grail of startup success. Who are these "unicorn companies," Lee wanted to know, and what traits do they share?

Lee and her team at Cowboy Ventures crunched numbers to come up with some interesting conclusions, including that twentysomething founders are uncommon among American unicorns and that big pivots are very unusual among them. But did the design of Lee's intriguing investigation miss an important fact about this much coveted club of companies valued at a billion dollars or more each?

By design, all the companies Lee looked at were American--understandably, as that's her investment patch--but limiting her study to U.S. companies led her to conclude that "San Francisco (not the Valley) now reigns as the home of unicorns." But what if you widen the lens and look not just at American businesses but startups everywhere that have managed to cross the billion-dollar mark? Would either San Francisco or its neighbor Silicon Valley come out as a unique unicorn breeding ground?

Where Unicorns Are Really Born

A new study from Atomico, a London-based venture capital firm led by Skype co-founder Niklas Zennström, and reported in the Financial Times, suggests no. Rather than stick to just the 39 American unicorns that Lee looked at, Zennström and his team analyzed the 134 companies globally that have reached the billion-dollar mark over the past decade. Broadening the scope of the investigation revealed that neither Silicon Valley nor San Francisco, despite their dense startup ecosystems and reputations as incubators of top companies, dominate the unicorn club.

"The majority of tech startups that have gained a $1 billion valuation in the past decade hailed from outside Silicon Valley," the FT's

Murad Ahmed reports. The study found "79 were from the U.S., with 52 from the Silicon Valley area, while 26 came from China and 21 from Europe." Latin America, the Middle East, and Africa are all still awaiting their first unicorn.

For Zennström the takeaway is clear. We "will see the proportion of major technology companies not hailing from the American West Coast rise over time," the FT says he concluded from his investigation. While other VCs disagree that Silicon Valley will lose its luster as the world's preeminent startup hub anytime soon (and also point out that as companies grow they very often quickly open California offices), the dispersed geographical roots of the world's most successful companies will probably cheer individual founders based outside Silicon Valley and San Francisco.

Whether founders hoping to make it big should move to Silicon Valley is much debated, but these results seem to support those that argue that the best place to build a successful business may be your home turf, with all its rich connections and in-depth local knowledge, wherever in the world that might be.

Do the results of Atomico's investigation surprise you?