Immigrants — they get the job done.

While the debate over America’s immigration policy has been stirred up again by President Trump requesting $8.6 billion from Congress to build a border wall with Mexico, and House Democrats introducing a bill to offer 2.5 million U.S. immigrants a chance at citizenship, a new study suggests that immigration boosts the economy in the short-term — and continues to do so even 100 years later.

Oxford researchers studied the effects of immigration in the U.S. between 1850 and 1920 — aka the Age of Mass Migration — and its effect on economy prosperity today. And they found that the counties with more historical immigration have overall higher incomes, less poverty and less unemployment even today. In fact, the immigration impact is so sizable that they calculate that increasing the percentage of historical immigrants in a county by just 4.9% results in a 13% increase in average per capita income today, as well as a 44% increase in average manufacturing output per capita from 1860-1920 (and a 78% increase in 1930); a 37% increase in farm values; and a 152% increase in the number of patents per capita.

See also: How immigration actually helps native-born U.S. workers

The Age of Mass Migration was notable not just for the sheer number of immigrants — an estimated 55 million Europeans migrated to the New World (North and South America and Australia) between 1850 and 1914, with the U.S. absorbing about 30 million of them — but also because that wave of newcomers included immigrants from Southern, Northern and Eastern Europe, whereas most previous immigrants had come from Western Europe.

And the resulting melting pot benefited local economies almost immediately, as the authors noted that the places with the most immigrants saw greater industrialization, agricultural productivity and innovation. That’s because the less-skilled immigrants, which made up the majority of the migrants, provided the labor force needed for industrial development, which spurred more and larger manufacturing plants and greater agricultural activity. Meanwhile, the smaller number of higher-educated skilled immigrant workers brought knowledge and skills that further boosted industry and productivity, and led to developing more patents.

The authors added that there was some social tension between the newcomers and the natives initially, but after 100 years, rates of crime and civic participation are now similar between the communities with a history of immigration, and those without.

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“What is fascinating is that despite the exceptionalism of this period in U.S. history, there are several important parallels that one could draw between then and now: the large influx of unskilled labor, the small but important inflow of highly skilled innovators, as well as the significant short-run social backlash against immigration,” said the paper’s lead author Sandra Sequeira in a statement. “There is much to be learned from taking a longer perspective on the immigration debate.”

The Migration Policy Institute puts the number of U.S. immigrants today at about 45.5 million, drawing on 2016 Census data. While concerns over immigration policy include the fear that the newcomers are a drain on local resources, a growing body of research suggests that the immigrants themselves are a valuable resource.

A 2018 French study of more than 30 years of data also found a link between an increase in asylum seekers who become permanent residents with benefits on the economy around four years later, such as an increase in the gross domestic product, a decrease in the unemployment rate and increased tax revenues.

See also:Economists say 30 years of data show asylum seekers are not a burden on European countries

Today, U.S. industries that provide food, shelter, clothing, transportation and health care depend on immigrant labor, according to the New American Economy (NAE) data provided to Axios, as the foreign-born workers take jobs that American-born workers often don’t take; they round out the workforce rather than taking jobs. For example, immigrants working as child care providers allow the mothers and fathers hiring them to also go to work. (It should be noted that the NAE supports immigration.)

Research finds 14% of nurses and almost a quarter of health aides in the U.S. are immigrants. monkeybusinessimages/iStock

The apparel manufacturing industry counts the highest share of foreign-born workers at 50%, Axios reports, followed by taxi and limousine services (49%), nail salons and personal care (46%), private household workers like cleaners and nannies (44%) and general food industries (42%). Additionally, 14% of nurses in the U.S. are immigrants, as are close to a quarter of health aides. More than a quarter of physicians and surgeons in Michigan are immigrants, the data found, as are about 15% of chefs and cooks in Nebraska, while 80% of the limo and taxi drivers in NYC are foreign-born.

And a 2017 National Academies of Sciences, Engineering and Medicine report that found immigration “has an overall positive impact on the long-run economic growth in the U.S.” While it concedes that first-generation immigrants cost the government more than native-born Americans do at about $1,600 per person, their children are “among the strongest fiscal and economic contributors to the U.S.” who wind up contributing about $1,700 per person per year (studies have shown they are more likely to complete college and are less likely to live in poverty than native-born Americans). In comparison, native-born U.S. citizens (including third generation immigrants) contribute $1,300 per year. PBS also reported that less-educated immigrants tend to work more than people with the same level of education born in the U.S.; about 70% of immigrants with no high school diploma work, compared with about half of all U.S.-born Americans with the same education level.

And high-skilled immigrants significantly increase innovation in the U.S., according to The Hamilton Project, a research group within the centrist Brookings Institution, which found that a “1 percentage point increase in the college-educated or advanced degree-holding immigrant shares of the U.S. population are estimated to produce a 12.3% or 27% increase in patenting per capita, respectively.”