Last year's rebound in technology added the highest number of jobs to the Bay Area since the dotcom boom of the late 1990s, according to a report released Tuesday.

Silicon Valley employment grew by 3.6 percent in 2012, more than double the rate of job growth in the United States and outpacing the rest of the Bay Area, according to the 2013 Silicon Valley Index, a summary of economic and social indicators produced by the Silicon Valley Community Foundation and the nonprofit Joint Venture Silicon Valley.

The Bay Area added 92,000 jobs in 2012, 42,000 of them in Silicon Valley, defined as Santa Clara and San Mateo counties, plus Fremont, Newark, Union City and Scotts Valley. San Francisco added 18,000 jobs in the same period.

"Silicon Valley is the first to emerge from the recession nationally, and we're leading some pretty prodigious growth for the nation," said Joint Venture CEO Russell Hancock in the group's 16th annual index.

However the local numbers continue to reflect a shrinking middle class, Hancock said. For the third year in a row, per capita income rose while median income fell.

"There are a lot of millionaires and billionaires and that raises our averages (reflected in per capita income)." he said.

"For decades, the Valley's most striking feature was a robust middle class and now we've become the classic hourglass economy."

While households earning more than $100,000 grew by 1 percent to account for 43 percent of the total, those earning less than $35,000 rose by 2 percent, comprising 20 percent, according to the index.

Food Stamp participation climbed to 5 percent in Silicon Valley -- but remained far below the more than 10 percent participation in California and 15 percent nationwide.

Driving Silicon Valley's growth in the last year were jobs in software, cloud computing, social media, Internet and information services and mobile device applications, Hancock said.

Hardware was flat. Research and development grew by 14.5 percent and the overall prosperity boosted jobs in law, accounting and even nonprofits, which were up by 3.3 percent, the index said.

Productivity in the Valley -- at $157,100 per employee -- also led the nation, and has grown every year since 2008.

Total Silicon Valley patent registrations ticked up, though represented a smaller portion of total statewide patents because of the rise of patents in other areas such as San Diego.

In a reversal from the previous year, the number of new firms opening spiked to 46,000, while 12,000 closed, Hancock said. There also was a 10 percent growth in sole proprietorships -- firms with no employees, just a single principal.

Silicon Valley venture capital investment declined, while San Francisco investment expanded, Hancock said.

That and other factors led Hancock and Silicon Valley Community Foundation CEO Emmett Carson to conclude that Silicon Valley should be redefined to include San Francisco.

"Today the case is that we're seeing a regional economy that's being created," said Carson, adding that regional -- not just local -- solutions are urgently needed if the Bay Area's 101 cities and towns are to effectively address pressing issues of traffic, housing and preparation for climate change.

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