In his State of the Union address, President Trump outlined the immigration reforms to be implemented in exchange for giving recipients of Deferred Action for Childhood Arrivals a path to citizenship. His plan required appropriations for the border wall, increased border security, an end to diversity visas (also known as the green card lottery) and new limits on immigrants’ access to family reunification.

If they were to become law, these reforms would drastically reshape the demographics of immigration to the United States. Family reunification, which its detractors call “chain migration,” generally accounts for about two-thirds of all legal permanent immigration to the United States, and the vast majority of these immigrants come from Latin America and Asia. The border measures would affect Latin American immigrants most broadly (most undocumented immigrants come from Latin America, with an increasing minority coming from Asia), and an end to the diversity visas would most affect Eastern European, African and Asian immigrants.

Although some immigration hard-liners claim the main goal of these restrictions is to protect native-born workers, others are openly seeking ways to reshape immigration policy in order to make the U.S. immigrant population less Latin American, African and Asian, and — to put it simply — more white. But they should be careful of setting their hopes too high. Immigration policy, especially when engineered to whiten the population, has a tendency to backfire.

Over the past century and a half, immigration restrictionists have tried many times to re-engineer the race and ethnicity of migrants to the United States. More often than not, in fact, national immigration legislation has been crafted in order to keep specific racial and ethnic groups out of the United States.

At the same time, however, these restrictionist policies never actually worked the way they were intended to — because they seldom dealt with the causes driving people to immigrate or with the factors that incentivized migrating to the United States. While some of them did block immigrants of certain nationalities, they also generated unintended consequences that were often the opposite of the results restrictionists had anticipated. ...