When Buck Gee was a vice president at Cisco Systems, he one day looked around his desk and noticed that he stood out in one key way: Gee was the only Chinese American executive in Cisco's U.S. product development group. In fact, there were very few Asian American executives at all.

Since then, Gee, who retired from Cisco in 2008, has been a man on a mission. Asians are generally well-represented in technology companies among the rank and file, but few ascend the corporate ladder to the top. Gee wants to change that.

The recent release of data on the diversity of employees by more than a dozen tech companies has lent new vigor to Gee's campaign to shatter what he calls the "bamboo ceiling."

He points to Yahoo, where Asians hold 17 percent of leadership positions while making up 39 percent of its U.S. workforce, according to demographic data the company released in June. Women - typically woefully underrepresented in technology - fared better. They make up just 37 percent of Yahoo's global workforce, but hold 23 percent of executive-level positions.

That pattern persists across most tech companies.

"If you look at the press, everyone points out that white men and Asian men dominate technology," Gee said. "That's mostly right, except that few Asians rise to the top."

Across the board, about 70 to 80 percent of top management positions are held by white employees.

When Gee noticed the issue, he wondered why he didn't have more peers at the top. There were plenty of Asian Americans working in technology - he and his colleagues didn't have the same barriers that block women, blacks or Latinos from entering the field. They had access to science and technology education, and there were no widely held beliefs that they were unsuited for high-tech gigs (in fact, it was the opposite).

It's a surprising disparity - plenty of Asian Americans make it into the pipeline, they just don't make it to the end of the pipe.

"A long time ago, Asians were considered the model minority," Gee said. "But certainly, at least in business, we're now the missing minority."

Others, like Thomas Sy, a professor at UC Riverside's Leadership and Group Dynamics Lab, were already studying the issue. The problem extends well beyond tech, to boardrooms and executive suites in many industries.

Root causes, he said, can be difficult to pin down. Part of it is cultural.

In a paper Gee published this year, he noted that factors preventing more Asian Americans from moving up the ranks include a traditional deference to authority, ineffective communication skills and an aversion to risk taking. Many Asians, he said, are brought up with an emphasis on acquiring skills and achievements, but not on the "soft skills" necessary for managing people at a high level.

But the biggest problem, said both Sy and Gee, is that no one seems interested in talking about the lack of Asians at the top.

"When you talk about developing minority leadership, everyone buys into it," said Sy. "But when minority is defined as an Asian American, there is head scratching. When I publish research papers, people always ask me why I don't focus on women or African Americans instead."

Recently, Gee crunched the numbers from Yahoo, Google, LinkedIn, Facebook, Intel and Twitter.

Google and Twitter were the only companies where Asian Americans had a better chance of achieving a leadership position than women. Asian American employees at LinkedIn, Yahoo, Facebook or Intel had a smaller probability of rising through the ranks than their female colleagues. For example, at LinkedIn, Asian Americans hold 60 percent of the company's technical jobs, but only 28 percent of its leadership positions.

"It is a big issue now, and it getting more pronounced," said Vish Mishra, a venture capitalist at Clearstone. "Many conversations are taking place in the executive suites and boardrooms these days and that's a good thing. I see plenty of bench strength among Asian leaders, but they are not given enough playing time."

At Cisco, Gee was the first to observe the problem. He began inquiring at other companies and found they had the same problem, too.

"They all just asked me the same question," he said, " 'What do we do?' "

One solution: Gee, who founded a five-day annual workshop at Stanford that focuses on teaching leadership to Asian Americans, will help close that gap.

"I want people to be aware there's an issue," he said. "And I'm doing it because no one else is."