To understand why the Twin Cities developed a big constellation of corporate headquarters, it helps to know a little bit about the experience of Greg Brew.

He came to the Twin Cities from Pasadena, Calif., where an hourlong freeway drive — on a good day — took him to work at a unit of BMW. Polaris Industries recruited him, and now he is the company's director of industrial design.

Eleven years into his Twin Cities experience, Brew said he has no intention of leaving.

What brought him to the Twin Cities included, of course, a good job offer. It also wasn't Detroit. But his list of why he stays is so long he struggled last week to quickly boil it down.

It includes performing arts, good schools and the endless opportunities for outdoor recreation. As he put it, "Minnesotans never shut down. They come home, change clothes, and keep going, no matter what the weather is."

As a manager, he's grown his team from about four people to more than 30, recruiting from as far away as ­Australia. And once here, Brew said, they also have stayed.

The unmarried people he's recruited might care about the drive time from Uptown in Minneapolis to Polaris in Medina. Staffers with young children likely have bought houses near each other in the western suburb of Maple Grove, which they call "the MG."

"Now we have a whole contingent really fired up about Robbinsdale," he said of the older first-ring suburb. "If you lived in L.A. you'd be locked into mile after mile of homogenous suburbia. What you have here is so much more texture. That part is kind of cool."

The story of Brew coming here and sticking around 11 years fits nicely with the work of Myles Shaver, a professor at the Carlson School of Management at the University of Minnesota. Shaver has been puzzling for years over the origins of the Twin Cities' big and vibrant corporate community — one of the largest concentrations of Fortune 500 companies in the country — and concluded that the explanation is people like Brew. Thousands of them.

His theory was that bright, hardworking middle managers, engineers and others stayed in town, maybe changing jobs but all along helping grow their employers into big companies. It was a virtuous circle, with growing companies providing great job opportunities for talented people who worked hard and then helped the companies grow even bigger.

But he needed data. And in a recent conversation, he shared plenty that confirms he's on very solid ground.

Shaver calls his case "a human capital story," and it's actually decades in the making. Since the inaugural Fortune 500 list in 1955, 39 of the 40 Twin Cities companies that made the list were homegrown. And none of the best conventional explanations for how that many big companies sprang up here seemed to apply.

It's not geography. It's darned cold here in the winter. As Shaver wryly noted, even some of the most popular cross-country airline routes don't come as far north as the Twin Cities. That means we can't even properly get called flyover country.

We also mostly don't have a bunch of different companies from the same industry all grouped around each other, with information seeping between them, one of the so-called cluster effects. That's what helped metropolitan Detroit grow back when the domestic carmakers were booming.

In greater Detroit, there are 14 Fortune 500 companies in seven industries. In the heart of Silicon Valley, San Jose, there are 12 Fortune 500 companies in six industries.

Here in the Twin Cities there are 19 Fortune 500 firms in Shaver's data, representing 15 industries. Medical device manufacturing comes to mind as a particularly vibrant local industry, but no one could argue that we have thriving clusters in 15 industries.

That mostly just left the people who worked here as his explanation for the area's growth of corporate headquarters.

When Shaver went out to gather information, he quickly heard that it's difficult to recruit anyone here from out of state. Once here, however, people are just as difficult to recruit back out.

For confirmation, Shaver looked at census data for the 2007 to 2011 period, comparing the Twin Cities with 21 other large metro areas. He wasn't interested in everybody, only people in management and the professions who might help grow a medium-sized business into a big one.

He decided that the best subset of that group was folks with at least a four-year college degree, a job, household income of more than $100,000 and with at least one child of school age.

For that group, the Twin Cities was only 19th as ranked by the rate they moved here. But once people got here, they really do stay. In this key group of professional people, the Twin Cities had the lowest out-migration of any of 22 big metro areas.

The trend has been the same for decades, paralleling the growth of the corporate community In 2000, the Twin Cities had the second lowest outflow of people of the major metro areas in this key group of professionals. In 1980, it was the lowest.

Shaver has lately been sorting additional details he's learned by ­surveying employees at big companies. While still early, he said it's going to be surprising for some people to learn how many Twin Cities headquarters employees have previously lived and worked someplace else.

As for what brought them here, he's not convinced by a popular theory of regional growth that it's great amenities, from outdoor recreation to bohemian cafes.

"That's actually backward," Shaver said. "That keeps people from leaving, but it doesn't attract them. It's about jobs."

Jobs like a design director at Polaris. A job worth moving from sunny California to do.

It should be pointed out, however, that Greg Brew's employer isn't yet on the Fortune 500 list. It was last ranked by Fortune at 621. As recently as two years previous, though, Fortune ranked it at 764. With revenue growing at double-digit rates, it shouldn't be long before it cracks the top 500.

And we will have one more convincing explanation for how that kind of business triumph was achieved.

lee.schafer@startribune.com • 612-673-4302