The average annual wage for high-tech workers in San Francisco rose to $156,518 in 2013, up almost 19 percent from the year before. That ranked the city No. 1 for high-tech wage growth out of 34 markets nationwide, according to Bureau of Labor Statistics data crunched by JLL, a commercial real estate services firm.

That number includes the value of stock options, meals and other benefits. JLL could not break out salaries alone.

The more astonishing statistic: The average tech wage on the mid-Peninsula (San Mateo County) last year was $291,497. Although that was down about 5 percent from 2012, it was still — by far — the highest average tech wage in the nation, surpassing Silicon Valley (Santa Clara County) by almost $100,000.

A likely explanation for the distortion: Facebook chief executive Mark Zuckerberg took only a dollar in salary but reaped $3.3 billion exercising Facebook stock options in 2013, up from the $2.3 billion option windfall he realized in 2012.

JLL got its numbers from the BLS Quarterly Census of Employment and Wages, which is a quarterly count of employment and wages reported by employers that can be broken down by industry at the county, state and national levels. To get an average wage, “We take all the aggregate wages in the tech sector and divide it by the number of (tech) jobs,” said Amber Schiada, JLL’s director of research for Northern California.

No one knows how much Zuckerberg contributed to aggregate wages in San Mateo County last year, but if you remove $3.3 billion from the total, you end up with an average tech wage of roughly $210,000. That’s still high, but more in line with Santa Clara County, where the average tech wage was about $196,000 last year.

This illustrates how outliers can distort averages. Schiada said the wage median (the midpoint in a sequence of numbers) would better reflect a typical worker’s income, but she did not have the data needed to construct a median.

The average wage in her report is for workers employed in a particular city or county, regardless of where they live. Schiada said that when Facebook moved its headquarters from Palo Alto across the county line into Menlo Park in late 2011, it distorted all sorts of regional jobs data.

As for San Francisco’s big increase in wages last year, it’s probably not Twitter. Although it went public in 2013, most of its employee stock options were not unlocked until 2014.

It probably results from a growing number of tech companies chasing a limited pool of programmers, engineers and other workers. San Francisco “is still largely anchored by finance and legal. Tech only makes up 20 percent of the office leasing market, but they are currently making up a good chunk of the demand,” Schiada says. “About 40 percent of tenants looking for space is tech companies.”