Here’s a good starting point for a rational debate on immigration (if that’s even possible now)

Immigration debate shouldn’t be off limits.
Immigration debate shouldn’t be off limits.
Image: Reuters/Monica Almeida
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In the US or Europe, any argument about immigration—and there have been many—has to start with one basic fact: The share of foreign-born workers in these places has risen tremendously over the last 60-plus years. 

The chart above tracks the percentage of foreign-born residents of the US and UK since 1950; the figures include documented and undocumented residents. Exact statistics do not go back as far for other developed nations, but the recent spike in immigrants has been common across most of the rich world. United Nations data show that since 1990, the foreign-born population grew from 7.2% to 11.2% in developed countries, while immigration to developing countries remained constant.

As a result, while the ethnic compositions of most developed countries once were relatively static, they are now changing rapidly. For those who lived through the 1960s and 70s, the current level of immigration might reasonably feel dizzying.

From an aggregate human welfare perspective, the increase in international migration is a very good thing. Immigration from a poor to a wealthy country is perhaps the most effective known anti-poverty measure. It also increases global productivity by allowing more people to work in high-technology countries.

There is—or at least there ought to be—little debate that overall, welcoming immigration has at least a modest positive effect on economic growth. At the most basic level, more people means more economic output and more consumers. Immigrants also tend to be of a working age, and thus particularly productive. They also are unusually entrepreneurial, while concerns that immigrants use too many government resources are demonstrably overblown (pdf).

A more contested question is whether immigrants decrease the wages of those already in a given country.

Basic economic theory suggests that an increase in foreign workers should reduce the wages of native workers who have similar skills. Economists from Wellesley College and Harvard University find that most empirical studies show only minor negative impacts of immigration on the wages of natives. But they note that the size of the effect is highly disputed.

The most influential of the immigration skeptics is the Harvard economist George Borjas—an immigrant himself. While Borjas grants that, overall, immigration increases incomes, his research suggests that immigrants significantly depress the incomes of natives with similar skills. Specifically, Borjas estimates that a 10% increase in the number of immigrants in a particular skill group leads to a 3% to 4% decrease in wages among that group.

Yet there also are winners—not just the immigrants themselves but also native workers who are business owners or who have complementary skill sets to the newcomers.

And for many people, the impact of immigrants can cut both ways. For instance, native-born doctors would be hurt by a flood of immigrant doctors competing for jobs and patients. But they would be helped by an influx of immigrant farmers who make the doctors’ food cheaper and pay the doctors for services.

The debate over immigration has figured into the vote for Brexit, the rise of Donald Trump, and the lead-up to elections in France and Germany. Unfortunately, just as the topic is gaining in importance, political polarization is making it increasingly difficult to talk about, with discourse often overrun by simple, and frequently hateful, rhetoric. It makes for some great sloganeering, but it doesn’t do justice to the complexities of the issue.