Europeans' support for refugees of varying background is stable over time.

Protracted global conflicts during the past decade have led to repeated major humanitarian protection crises in Europe. During the height of the Syrian refugee crisis at the end of 2015, Europe hosted around 2.3 million people requesting asylum1. Today, the ongoing war in Ukraine has resulted in one of the largest humanitarian emergencies in Europe since World War II, with more than eight million Ukrainians seeking refuge across Europe2. Here we explore whether repeated humanitarian crises threaten to exhaust solidarity and whether Europeans welcome Ukrainian asylum seekers over other asylum seekers3,4. We conducted repeat conjoint experiments during the 2015-2016 and 2022 refugee crises, asking 33,000 citizens in 15 European countries to evaluate randomly varied profiles of asylum seekers. We find that public preferences for asylum seekers with specific attributes have remained remarkably stable and general support has, if anything, increased slightly over time. Ukrainian asylum seekers were welcomed in 2022, with their demographic, religious and displacement profile having a larger role than their nationality. Yet, this welcome did not come at the expense of support for other marginalized refugee groups, such as Muslim refugees. These findings have implications for our theoretical understanding of the drivers and resilience of public attitudes towards refugees and for policymakers tasked to find effective responses to the enduring stress on the asylum system5-8.

How membership in the North Atlantic Treaty Organization transforms public support for war.

How do military alliances affect public support for defending targets of aggression? We studied this question by fielding an experiment on 14,000 voters in 13 member countries of the North Atlantic Treaty Organization (NATO). Our experiment involved a hypothetical scenario in which Russia attacked a target country. We randomly varied the identity of the target (Bosnia, Finland, Georgia, or Sweden), and whether the target was a member of NATO at the time of the attack. We found that voters in every member country were far more willing to use military force to defend each target when the target was in NATO, than when the target was outside the alliance. The expansion of NATO could, therefore, transform European security by altering the likelihood and scale of future wars. We also uncovered important heterogeneity across targets: the benefits of joining NATO were considerably larger for Bosnia and Georgia than for Finland and Sweden, since most voters in NATO countries would defend Finland and Sweden even if they remained outside the alliance. Finally, the effect of NATO was much stronger among voters who perceived NATO as valuable for their own country. Rhetorical attacks on NATO could, therefore, undermine the alliance by eroding the public's willingness to defend other members, whereas rhetoric highlighting the benefits of NATO could bolster defense and deterrence. These findings advance knowledge about the effects of alliances, while also informing policy debates about the value and size of NATO.

Improving refugee integration through data-driven algorithmic assignment.

Developed democracies are settling an increased number of refugees, many of whom face challenges integrating into host societies. We developed a flexible data-driven algorithm that assigns refugees across resettlement locations to improve integration outcomes. The algorithm uses a combination of supervised machine learning and optimal matching to discover and leverage synergies between refugee characteristics and resettlement sites. The algorithm was tested on historical registry data from two countries with different assignment regimes and refugee populations, the United States and Switzerland. Our approach led to gains of roughly 40 to 70%, on average, in refugees' employment outcomes relative to current assignment practices. This approach can provide governments with a practical and cost-efficient policy tool that can be immediately implemented within existing institutional structures.

How economic, humanitarian, and religious concerns shape European attitudes toward asylum seekers.

What types of asylum seekers are Europeans willing to accept? We conducted a conjoint experiment asking 18,000 eligible voters in 15 European countries to evaluate 180,000 profiles of asylum seekers that randomly varied on nine attributes. Asylum seekers who have higher employability, have more consistent asylum testimonies and severe vulnerabilities, and are Christian rather than Muslim received the greatest public support. These results suggest that public preferences over asylum seekers are shaped by sociotropic evaluations of their potential economic contributions, humanitarian concerns about the deservingness of their claims, and anti-Muslim bias. These preferences are similar across respondents of different ages, education levels, incomes, and political ideologies, as well as across the surveyed countries. This public consensus on what types of asylum seekers to accept has important implications for theory and policy.