Immigration to the United States has consistently offered a route to escape poverty — if not for poor immigrants themselves, then for their sons.

New research linking millions of fathers and sons dating to the 1880s shows that children of poor immigrants in America have had greater success climbing the economic ladder than children of similarly poor fathers born in the United States. That pattern has been remarkably stable for more than a century, even as immigration laws have shifted and as the countries most likely to send immigrants to the United States have changed.

The adult children of poor Mexican and Dominican immigrants in the country legally today achieve about the same relative economic success as children of poor immigrants from Finland or Scotland did a century ago. All of them, in their respective eras, have fared better than the children of poor native-born Americans. If the American dream is to give the next generation a better life, it appears that poor immigrants have more reliably achieved that dream than native-born Americans have.

The findings, published in a working paper by a team of economic historians at Princeton, Stanford and the University of California, Davis, challenge several arguments central to the debate over immigration in America today. The Trump administration has moved to reorient the country’s legal immigration toward wealthier immigrants and away from poorer ones, arguing that the nation can’t afford to welcome families who will burden public programs like Medicaid. This research suggests that immigrants who arrive in poverty often escape it, if not in the first generation then the second.