The unique diversity of Silicon Valley is not reflected in the region’s tech workplaces — and the disparity is only growing worse.

Hispanics and blacks made up a smaller share of the valley’s computer workers in 2008 than they did in 2000, a Mercury News review of federal data shows, even as their share grew across the nation. Women in computer-related occupations saw declines around the country, but they are an even smaller proportion of the work force here.

The trend is striking in a region where Hispanics are nearly one-quarter of the working-age population — five times their percentage of the computer work force — and when dual-career couples and female MBAs are increasingly the norm.

It is also evident in the work forces of the region’s major companies. An analysis by the Mercury News of the combined work force of 10 of the valley’s largest companies — including Hewlett-Packard, Intel, Cisco Systems, eBay and AMD — shows that while the collective work force of those 10 companies grew by 16 percent between 1999 and 2005, an already small population of black workers dropped by 16 percent, while the number of Hispanic workers declined by 11 percent. By 2005, only about 2,200 of the 30,000 Silicon Valley-based workers at those 10 companies were black or Hispanic.

The share of women at those 10 companies declined to 33 percent in 2005, from 37 percent in 1999. There was also a decline in the share of management-level jobs held by women.

“It’s just disappointing,” said Shellye Archambeau, the African-American CEO of MetricStream, a Palo Alto-based company that provides governance, risk and compliance support to global corporations such as BP and Pfizer. “The valley is a very strong place, but the fact that we are so lacking in female leadership, in African-American leadership, and frankly in Latino leadership in tech, you just sit there and say, ‘Imagine what it could be.’ “

With the number of white computer workers also dropping after 2000, Asians were the exception. They now make up a majority of workers in computer-related occupations who live in Silicon Valley, although they hold only about one in six of the nation’s computer-related jobs.

Among the findings:

Of the 5,907 top managers and officials in the Silicon Valley offices of the 10 large companies in 2005, 296 were black or Hispanic, a 20 percent decline from 2000, according to U.S. Department of Labor work-force data obtained by the Mercury News through a Freedom of Information request.

In 2008, the share of computer workers living in Silicon Valley who are black or Latino was 1.5 percent and 4.7 percent, respectively — shares that had declined since 2000. Nationally, blacks and Latinos were 7.1 percent and 5.3 percent of computer workers, respectively, shares that were up since 2000, according to the U.S. Census Bureau.