Leah Boustan on debunking immigration myths with data

As a teenager growing up in Massachusetts, Boustan often heard stories from her family about their Jewish ancestors’ immigration to the United States. Her father gave a dramatic account of his own grandfather’s flight from the Russian Empire: after stuffing some books in a knapsack, he fled while the Czar’s men pursued him on horseback.

The story was compelling, but Boustan wondered how much of it was rooted in fact. “I thought, really?” she said in an EGC interview. “I wondered whether some of the stories we heard in my family and in the Jewish community in general were a little too stylized.”

As an undergraduate at Princeton, she discovered the power of data to answer social and historical questions. “What I found magical was the ability to collect and create datasets on nearly any social topic of interest,” she said, reflecting on a course in applied econometrics. “To me, this was revelatory.”

The appeal of using empirical methods to evaluate historical myths led Boustan to focus on economic history during her economics PhD at Harvard. Her dissertation studied the effects of black migration from the American rural south to northern cities following World War II. Using demographic and house price data, Boustan investigated so-called “white flight” from urban areas to the suburbs. While the prevailing narrative suggests that this trend stemmed from white people’s distaste for living in diverse neighborhoods, her analysis revealed another key driver: the (mostly white) middle class’s desire for political autonomy. The suburbs allowed white people to avoid sharing local government and public school systems with urban blacks. 

Boustan also investigated the economic effects of black migration during this period. She found that the influx of black migrants from the south lowered wages for northern-born black workers, while having no effect on white wages – an effect that ultimately slowed average black economic growth.

After completing her PhD, Boustan began her academic career at UCLA before returning to Princeton as a professor. Her research turned to examining historical narratives surrounding immigration to the United States – particularly during the so-called Age of Mass Migration, when more than 30 million European immigrants arrived on US shores between roughly 1880 and 1920. 

In one paper, for instance, Boustan analyzed a topic close to her family’s own story: how did economic factors impact Jewish emigration from the Russian Empire to the United States? The prevailing theory has long been that political persecution was the principal driver. But after examining labor, wage, and demographic data, Boustan found that American economic conditions motivated Jewish migration perhaps just as strongly.

In another paper, Boustan and coauthors – including Ran Abramitzky, a Stanford professor of economics who became a longtime collaborator and friend – studied the economic returns to migration from Norway to the United States during the same period. Comparing male immigrants’ earnings to those of their brothers who remained in Norway, they found that the returns to migration were just 70%, compared to an estimated 200% to 400% for immigrants from Mexico to the United States today. Studying brothers helped isolate the effects of immigration from other potential causes – for instance, that the people who immigrated had greater human capital and earnings potential.

In 2018, during the first Trump administration, Boustan and her coauthors found their work in the political spotlight when the President made an offhand comment that he wished for “more people from Norway” to immigrate to the United States. All of a sudden, journalists were seeking out researchers who had studied immigration from Norway.

“That got us thinking that we may have something to say about immigration past and present,” recalls Boustan. “We thought maybe we should write something for the public – to translate the work we’ve been doing for ten years for the general-interest reader.

In their 2022 book Streets of Gold: America’s Untold Story of Immigrant Success, Boustan and Abramitzky use historical and more recent Census data to evaluate immigrant families’ economic mobility and cultural integration. In particular, they debunk the myth that today’s immigrants to the United States are less upwardly mobile than during prior generations – directly addressing the subtext of Trump’s comment. 

For instance, Boustan and Abramitzky analyze “earnings convergence,” or the pace at which immigrants’ earnings catch up to those of native-born workers. They find that the rate of earnings convergence in the United States has essentially remained the same since the late 18th and early 19th centuries. Among immigrants who arrived between 1970 and 2000, the average earnings gap with native-born workers narrowed from around 30% to 16% during the twenty years after their arrival – similar to the rate of convergence experienced by European immigrants during the Age of Mass Migration.

Notably, however, the researchers do not find evidence of full convergence in either period. 

“Neither in the past nor today do immigrants themselves completely close the earnings gaps with the US-born,” said Boustan. “The real success story for immigrants in the United States are their children.

Later in the book, Boustan and Abramitzky analyze the economic outcomes of immigrants’ children, similarly comparing recent data to historical periods. Using linked Census data which traces individuals and families across time, they focus on children raised at the 25th percentile of the annual income distribution (approximately $31,000 today). Overall, they find that immigrants’ children climb the economic ladder at roughly the same pace as second-generation children from earlier decades. On average, sons of immigrants surveyed in 1880 and 1910 reached the 45th to 50th percentile of the income distribution in adulthood, while children of immigrants today reach the 51st percentile.

They also find that immigrants’ children, both today and in the past, outperform children of US-born parents from equivalent backgrounds. In both eras, children of native-born parents raised at the 25th percentile of the income distribution reached just the 40th to 45th percentile in adulthood. Boustan sees this as one of her most surprising findings from decades of studying immigration – it challenges deeply held assumptions from across the political spectrum.

“People on the left might worry that immigrants and their children face discrimination, and people on the right might worry that immigrants and their children are unable to earn much because they don’t have the right attributes,” she said. “But it turns out that neither of those fears are true! In fact, children of immigrants today are just as successful in their degree of upward economic mobility as immigrants’ children in the past.

In Streets of Gold, Boustan and Abramitzky also attempt to quantify a less tangible aspect of immigrants’ lives: their integration into American society. To analyze such a complex question, they take the unique approach of tracking the names that immigrant parents give their children. As Boustan notes, immigrants’ naming choices can signal many different things, including attachment to their national or ethnic identity, their openness to integration, or their adaptation to American cultural norms. 

Again using Census data, Boustan and Abramitzky construct a “foreignness index,” which scores names based on the likelihood that they are given to foreign-born versus US-born Americans. The score for a given name can change over time, reflecting how names considered foreign in one era can become common in another, or how common names can fall out of fashion. In the 1990s and 2000s, for instance, names like Logan and Ashley were ten times more likely to be given to children of US-born parents than children of immigrants, receiving average foreignness scores of close to zero. On the other hand, names that have long been popular in the United States, like John and Elizabeth, were more evenly split between immigrant and US-born parents during this period – receiving average foreignness scores closer to 50.

Using this index, the researchers find that immigrants are more likely to give their children “American-sounding” names (i.e., names like John or Elizabeth in the example above) the longer they remain in the United States. On average, US-born mothers select names with an average foreignness score of 35. By contrast, immigrant mothers who give birth within the first three years of arriving in the United States pick names with an average score of 55. However, for immigrant mothers who have spent twenty years in the country, the average score drops to 45 – halving the “naming gap.” 

“It’s difficult to know what the exact psychological process is behind these trends, but it’s neat to see how immigrant parents choose different names for their kids as they spend more time in the country,” Boustan said. “It almost encapsulates the whole assimilation process in one outcome.

In the coming years, Boustan plans to expand the scope of her research beyond the United States. Working with researchers from around the world, she is studying contemporary differences between immigration to both the United States and to Europe. By comparing the upward mobility of immigrants to the United States with that of immigrants to different European countries, she seeks to understand differences in immigrants’ life trajectories across countries. In addition to economic outcomes, she is also studying the political response to immigration across countries – for instance, by comparing rhetoric from Congressional speeches in the United States to that of eight parliaments in Europe and the UK. 

For Boustan, these emerging research projects make her scholarship increasingly relevant to today’s public policy debates around immigration.  

“Now, for the first time, a number of European countries are 14% or more foreign-born – the percentage of foreign-born in the United States at the peak of the Age of Mass Migration,” she said. “We hear stories in the media about how there are all kinds of problems with immigration in Europe, but is this really true? What does it look like in the data? It’s bringing my research more into the modern day.”