In a reversal of a decades-old trend, China has replaced Mexico as the country sending the most immigrants each year to California, new data show.

About 33,000 immigrants moved to California from China last year, roughly triple the number who came in 2005, according to data from the U.S. Census Bureau and the Public Policy Institute of California. The number of immigrants coming to California from Mexico fell from almost 100,000 in 2005 to just over 30,000 in 2014, a roughly 70 percent decline.

Last year marked the second in a row that more residents arrived in California from China than from Mexico. India, which sent about 29,500 immigrants to California last year, also is poised to overtake Mexico. Some of California’s recent Asian arrivals are college students or long-term workers who eventually may leave the country; others will stay permanently.

The change comes as politicians debate immigration reform – who gets to come and who gets to stay – at all levels of U.S. government. Several presidential candidates this year have called for restricting immigration for economic or security reasons.

Donald Trump, who is leading most Republican presidential polling, has proposed building a massive wall to fortify the U.S. border with Mexico. Such a measure today would not affect the bulk of immigration to California: Less than a quarter of the immigrants arriving here last year, whether legally or illegally, came from Latin America, census figures show.

“One thing is for sure: The era of mass migration from Mexico is over,” said Karthick Ramakrishnan, professor of public policy at the University of California, Riverside, adding that more Californians are likely returning to Mexico each year than coming.

Emigration from Mexico has plummeted in recent years in response to several factors: the deep economic recession of 2007 to 2009; falling Mexican fertility rates; increased border enforcement; a rise in deportations; and declines or limited growth in the California jobs traditionally held by Mexican immigrants, including construction work and service-sector employment.

“For the next 10 years, there will be a shrinkage of new Mexicans in the workforce,” said Giovanni Peri, professor and chair of the economics department at UC Davis. “That trend is clearly set.”

Meanwhile, emigration from China and other Asian countries has grown largely because of increased demand for highly skilled workers, particularly in the technology industry. Arrivals from Asia have disproportionately settled in and around Silicon Valley, census figures show.

Many Asian immigrants have come to America on H-1B visas, which allow companies to temporarily hire foreign workers when there is a labor shortage. Some immigrants who obtain those visas eventually secure sponsorship from American companies and are able to stay permanently.

Supporters of the H-1B program, including many Silicon Valley companies, say it is vital to finding specialized talent; detractors have countered that the program takes jobs from U.S. workers.

“Our labor market is increasingly demanding more highly educated workers,” said Hans Johnson, a senior fellow at the nonpartisan Public Policy Institute of California. “Employers are increasingly finding those workers abroad.”

China also is sending many more students to America, and particularly California, to attend college. The state’s public colleges have dramatically increased the number of foreign-born students on their campuses. The number of international freshmen enrolling at University of California rose almost sixfold from 1,048 in 2009 to 6,071 in 2015, system data show.

Those students pay a higher rate of tuition than students from California. At UC Davis, international students pay about $39,000 in tuition and fees, compared with roughly $14,000 paid by in-state students. University officials have defended the higher foreign enrollment and fees, saying they help bolster funding after years of budget cuts.

In addition, the state’s prestigious private universities draw thousands of Asian students. Stanford’s undergraduate international student enrollment increased by more than 40 percent from 2005 to 2014, university statistics show.

About one-fourth of emigrants from China from 2012 to 2014 were between ages 18 and 24 and enrolled in college, census figures show. About a third of these students stay in America after college, Peri said.

“Most of these students do the science, tech, math degrees,” he said.

At UC Davis, the number of international freshmen rose more than tenfold from 91 in 2009 to 1,073 in 2015.

Samuel Yu, a junior majoring in chemistry at UC Davis, said his parents came to California from China in 2004, largely so he could attend an American college. He said it is hard to find a spot in a prestigious Chinese college because space is limited and the pool of applicants huge.

“The U.S. has a better education system than what China is developing,” he said.

Kenneth L. Lee, CEO of OCA-Asian Pacific American Advocates, formerly called the Organization of Chinese Americans, said many Chinese “families have saved everything to put into that one child” coming to the United States to study and earn a valuable degree.

“If you have one child, and you want to have your child do well, you say, ‘I am going to do everything I can to get in,’ ” he said.

Thousands of Chinese immigrants coming to California, though, are not in college or working in Silicon Valley. They are family members of Californians who have been in America for years. More than a quarter of Chinese immigrants to California from 2012 to 2014 were age 50 and older. The reunification visas that allow them to come and stay are in limited supply and can take more than a decade to obtain, Lee said.

U.S. census numbers do not distinguish between immigrants who are here legally and those here without authorization. Demographic experts said the majority of Chinese immigrants have gone through the immigration process; but “you have seen a pretty significant jump in undocumented immigration from Asia,” said Ramakrishnan. These immigrants typically overstay their visas.

The growth in Asian migration is a relatively young trend. Hispanics still far outnumber Asians in California, and likely will for a long time. About 5.3 million Asians live in California compared with 15 million Hispanics, census figures show.

But Chinese and other Asians increasingly lead the state’s cities and hold statewide offices. They own a growing number of businesses. And Asians were the largest ethnic group in the University of California’s 2015 in-state freshman class.

“If this persists, it will change California,” Johnson said. “The fastest-growing group would become Asian.”

The trend also may change the national conversation about immigration. The same trend playing out in California – more immigrants arriving from Asia than Latin America – is happening across the country, according to the U.S. Census Bureau.

“We are so used to thinking about what immigration looked like,” Ramakrishan said. “We just assumed the past would look like the future.”