As the threat looms of a trade war between Washington and Beijing, a new report finds that Chinese investment in the United States plunged by more than a third last year, a result of policy changes in both capitals.

That downward trend, if it continues, could have big implications for California.

No other state has received as much investment from Chinese companies, which since 2000 have sunk an estimated $21 billion into opening Silicon Valley technology labs, buying or funding local companies, and financing real estate development.

Chinese investment in U.S. companies and properties soared in the past decade, from less than $1 billion per year before 2008 to $46 billion in 2016. But according to the new report from the National Committee on U.S.-China Relations and the Rhodium Group, investment tumbled to $29 billion in 2017.

And that number was propped up by deals announced in 2016 but completed last year. Remove those, and the value of new Chinese investments in 2017 dropped 90 percent, according to the report — and fewer new deals were announced in 2017 than in 2016.

The trend means that American companies may not be able to attract as much investment as they otherwise could, potentially limiting their growth.

The authors lay the blame squarely on decisions made by government officials in both countries — not market changes.

In China, government authorities sought to rein in “irrational” international investments by companies overextending themselves and posing a risk to the country’s financial system.

Meanwhile, in Washington, proposed deals came under much more aggressive scrutiny from the Committee on Foreign Investment in the United States, which reviews foreign purchases of U.S. companies for potential threats to national security.

Starting under President Barack Obama and accelerating under President Trump, some federal officials have charged that the Chinese government has encouraged Chinese companies to buy or invest in American businesses as a way to obtain trade secrets and dominate key industries, particularly in technology. According to the report, an “unprecedented” number of Chinese-American deals were delayed or blocked by CFIUS in 2017.

As a result, some in Washington will likely welcome the drop in Chinese investment, said Stephen Orlins, president of the National Committee on U.S.-China Relations. He does not share their view.

“There are folks in the security community who think it’s a wonderful thing,” Orlins said. “There are folks in China who believe the state should interfere in investments, and they think it’s a wonderful thing. I think the majority of the American people and the majority of the Chinese people would say it’s not a good thing.”

Both governments are now threatening punitive tariffs on each other’s goods, from dishwashers to soybeans. And yet the world’s two largest economies remain tightly linked.

A companion report also issued by Orlins’ committee and the Rhodium Group shows that Chinese investment in American companies has spread across the country. Companies with at least 50 percent Chinese ownership now employ about 139,600 people in full-time positions across the United States, with the number growing by 7,400 employees last year.

California has been the biggest recipient, followed by New York and Massachusetts. The Golden State has an estimated 530 Chinese-owned businesses, with 16,000 jobs, compared with roughly 200 businesses in New York employing 6,440 people.

Within California, most of the money has flowed to the Bay Area and the Los Angeles region. Chinese businesses such as Internet search giant Baidu and telecom equipment-maker Huawei have opened labs in Silicon Valley to tap the region’s engineering talent. Chinese investors have also bought some firms outright, such as digital imaging company OmniVision, and purchased minority stakes in others, such as social networking business Snap.

Not all of the investments have panned out. As the report notes, LeEco — once described as the Netflix of China — had to sell its U.S. headquarters in Santa Clara last year, as the company scaled back after years of rapid international expansion.

The Bay Area has also actively courted Chinese investment. San Francisco has a public-private partnership organization, ChinaSF, that tries to facilitate Chinese investments in the city and the region, while also helping Bay Area companies expand to China.

“Other cities have come to us and said, ‘Hey, what’s your secret sauce?’” said Darlene Chiu Bryant, the group’s executive director. She is not particularly worried about last year’s drop in investment, saying, “It’s a time when the market levels off a bit, so I’m not surprised.”

Chinese investment in the Bay Area’s tech industry troubles critics who see in it a danger to America’s economic future. It is, they say, another way to gain access to intellectual property that China can use to seize the lead in such fields as renewable energy and electric or autonomous cars — property that the U.S. government has at times accused China of stealing outright.

“China has engaged in a wide-ranging, well-funded effort to direct and support the systematic investment in, and acquisition of, U.S. companies and assets to obtain cutting-edge technology, in service of China’s industrial policy,” read a report issued in March by the Office of the United States Trade Representative, arguing for tougher trade policies toward the country.

“China’s acts, policies, and practices are unreasonable because they are directed and supported by the government, and unfairly target critical U.S. technology with the goal of achieving dominance in strategic sectors,” the report read.

Bryant considers that fear overblown.

“At the end of the day, every tech company I know of wants to become a global company,” she said. “This is a global economy. Your technology is going to leave this country one way or another, it’s just a question of whether you’re going to be part of that transfer.”