With the debate over immigration to the U.S. as fiery as ever, a new analysis suggests that Silicon Valley would be lost without foreign-born technology workers.

About 71 percent of tech employees in the Valley are foreign born, compared to around 50 percent in the San Francisco-Oakland-Hayward region, according to a new report based on 2016 census data.

Immigrant techies tend to go to “the center of the action,” Seattle venture capitalist S. “Soma” Somasegar told the Seattle Times.

And Silicon Valley remains the “center of the tech universe,” according to the newspaper.

Beyond personal preferences, and the sheer number of companies in areas such as Silicon Valley and fast-growing Seattle, the financial resources of major technology firms also play a role in bringing in immigrants, the Seattle Times reported Wednesday.

Many foreign tech workers are employed under the controversial H-1B visa — intended for specialty occupations — which has become a flashpoint in the U.S. cage fight over immigration, with opponents claiming it lets foreigners steal American jobs. Several companies and UC San Francisco have been accused of abusing the visa program by using it as a tool to outsource Americans’ jobs to workers from far-away lands.

Although 2016 data released by the federal government last year showed that outsourcing companies — mostly from India — raked in the bulk of H-1B visas, Google took more than 2,500 and Apple took nearly 2,000 to hire foreign workers, about 60 percent of them holding master’s degrees.

Large companies, the Seattle Times pointed out, are better equipped to bring in workers under the H-1B.

“The H1-B process is not just complicated — it’s also quite expensive to sponsor an H1-B visa worker, a cost larger companies may be more willing to absorb,” the paper reported.

Legal blog UpCounsel puts the cost of the H-1B process at $10,000 to $11,000 per employee.

The Seattle Times did not include in its report a breakdown for Silicon Valley of how many foreign-born tech workers are U.S. citizens, versus visa holders. But the paper’s research indicated that 63 percent of Seattle’s foreign-born tech workers were not American citizens.

Backlash against the H-1B visa has been one part of the furor over U.S. immigration policies that has grown since President Donald Trump began campaigning for the presidency on an anti-immigrant platform. Fissures have widened in public opinion over Trump’s so-called “Muslim ban” on immigrants from Muslim-majority countries, over the admission of refugees, and over the unresolved fate of DACA, the program that has let millions of foreign citizens — brought to the U.S. illegally as children — remain in the country.