Immigrants to Switzerland who became naturalized citizens saw their earnings rise significantly compared to those who did not obtain the passport, a study showed Wednesday.
Average annual earnings were 13.5 percent greater for immigrants 15 years after they narrowly won naturalization through a local referendum, equal to about 5,500 Swiss Francs ($5,500), against immigrants who lived in the country but were unable to obtain nationality.
"These findings support the argument that citizenship can alleviate some of the labor-market discrimination that impedes immigrant integration," wrote the authors of the paper that appeared in the journal Science Advances.
Dominik Hangartner, an associate professor of public policy at ETH Zurich and one of the study's co-authors, told AFP that some employers saw citizenship as a credential that an immigrant plans to stay in Switzerland.
"At least some employers treat this as signal that these are people who are successfully integrated," he said.
Switzerland was a particularly useful country to study because of its system of naturalization referendums, in which residents of cities or towns vote to decide whether immigrants should receive the status.
The system is used by around a third of the country's more than 2,000 municipalities.
In 46 German-speaking municipalities, until 2003, these votes were held by secret ballot as opposed to a show of hands, allowing the researchers to access the ballots and determine who won citizenship by a narrow margin and equally who lost it by a narrow margin.
They combined this with data from the applicants' mandatory pension contributions to find people who were economically comparable at the start of the so-called "natural experiment" and to track how their income changed.
The researchers wrote that looking at applicants who narrowly won or lost the status through this process allowed them to eliminate selection bias, "since such close cases can be tipped one way or the other by current events or even the weather and are essentially arbitrary" or in effect randomly assigned.
The team looked at almost 4,000 applicants for naturalization between 1970 and 2003.
Winning citizenship proved especially beneficial for marginalized groups such as immigrants from Turkey and Yugoslavia, who saw their earnings rise by an average of 10,000 Swiss Francs annually over the 15 years.
"What citizenship does is that it helps to come closer to what Swiss natives with similar education and similar productivity would earn," said Hangartner, and it helped strengthen communities by increasing tax revenues and reducing welfare spending.
"Citizenship does help to get closer to closing the gap," he said.