In a feature story from the October issue of San Francisco magazine, Farhad Manjoo—the Wall Street Journal’s new tech columnist—offers a forcefully optimistic vision of how the tech industry’s growth “can benefit us all.”

Just don’t call it a “boom.”

The very word connotes unsustainability, a what-comes-up-must-go-down foreshadowing of trouble. It carries the threat of immediate displacement, the forced exodus of an entire class of people who lacked the foresight to pursue a computer science degree. Then, too, it’s associated with an undercurrent of suspicion: The techies are taking us for a ride. San Francisco has been a boomtown from the beginning, and we all know how that movie ends.

Rather, to understand the “depth and complexity of the latest tech revival” says Manjoo, “no economic stat tells the story better than the rising paychecks of workers in San Mateo County.”

At the end of 2011, according to the Bureau of Labor Statistics, people in the county just south of San Francisco earned about $81,000 a year on average. That’s a respectable figure—despite being a small, mainly suburban area, San Mateo had workers who were among the best paid in the nation. Then something extraordinary happened: Over the course of a single year, the county’s average pay shot up 107 percent. In the last quarter of 2012, San Mateo wage earners averaged about $168,480 a year. That made San Mateo by far the top-earning county in the nation, with paychecks more than 50 percent greater than those of the second county on the list—New York County, also known as Manhattan.

How did San Mateo workers get so rich so quickly? A little digging reveals that their rising fortunes were almost entirely attributable to a single event—Facebook’s IPO. In the spring of 2012, Mark Zuckerberg’s billion-user social network floated its stock on the NASDAQ. The IPO didn’t go well for retail investors—the share price languished in negative territory until August of this year—but the firm’s founders, investors, and employees cleaned up. Because the government’s calculation of average wages includes income from bonuses and stock compensation, the IPO windfall enjoyed by a few thousand workers at Facebook’s Menlo Park headquarters showed up in national statistics as a blessing bestowed upon the entire population of San Mateo.

In this single stat, then, lies the question at the heart of the Bay Area’s increasingly uneasy relationship with the tech industry: When workers at companies like Facebook and Google get rich, how widely are those gains shared across the local economy? In San Mateo, at least, the answer is clear. In part due to successes like Facebook, the county’s unemployment rate has hovered around 5 percent for much of the summer, and the size of the civilian labor force is close to a peak not seen since the late ’90s. The county’s coffers are flush—its new budget allocates hundreds of millions of dollars for improvements, including a new fire station, a new jail, new housing shelters, an overhaul of the county’s information technology systems, and a paydown of its pension liabilities.

But the “answer” may not be quite as “clear” as Manjoo would like.

According to recent study by a non-profit called Sustainable San Mateo County, the area lost thousands upon thousands of lower and middle income families between 2006 and 2011 (before Facebook’s May, 2012 IPO). Couldn’t that growing income gap also be a factor in San Mateo’s skyrocketing average pay and steady unemployment? An article about the study in the San Francisco Examiner described a “forced exodus” similar to the one Manjoo dismissed earlier:

San Mateo County shed more than 7,000 middle- and low-income households during a recent five-year period while the number of affluent ones grew by more than 10,000, according to a new study. [...]

Those low- and middle-income households didn’t simply get rich in the past five years, said Adrienne Etherton, the executive director of the nonprofit that conducted the study. More likely, she said, they’re leaving.

The apparent flight of the lower- income households and the influx of affluence to the county highlights the county’s ongoing concerns with highly competitive labor markets, education and affordable housing.

“People are pushed to other counties because it’s affordable to live there,” said Linda Asbury of the San Mateo Area Chamber of Commerce.

Rosanne Foust, president of the county’s Economic Development Association told the Examiner that “supply-and-demand” has also made affordable housing in the area “scarce." Venture capitalists like to talk about funding dropouts, but education still counts in the county’s competitive labor market:

“There is a highly educated workforce, and those that don’t have that higher-level degree may have to settle for lower-paying jobs,” she said.

With San Mateo County employers placing a premium on highly educated employees, it impacts who is employed.

“It’s a technology-driven world, especially the area we live in,” Foust said.

Manjoo wasn’t wrong to highlight rising paychecks in San Mateo as the best indicator of what kind of gains this tech “revival” will bring and to whom. The comparison to Manhattan was certainly apt. In fact, the concentration of rich neighborhoods sounds more and more like New York City every day.

To contact the author of this post, please email nitasha@gawker.com.

[Image via Getty]