Shared religion with the host majority makes immigrant integration substantially easier.

Evidence

This is significant because the religious-cultural gap is strongly correlated with an inability to assimilate. A comparative study of Christian and Muslim immigrants to Germany establishes that the integration of Muslims is substantially harder than the integration of Christians. Although the integration of Spaniards and Yugoslavs in Germany was prolonged and difficult by American standards, it nonetheless took place. Muslims experienced problems forming an ethnic identity in a country where the dominant religion is not Islam. Christian immigrants, by contrast, were able to take advantage of the religious background they share with the vast majority of Germans to integrate. — Michael A. Reynolds and Thomas D. Grant, The Future of Europe and Its Muslims, 101

Categorization

• DEEPTHINKING: The mechanism here — that religious congruence with the host majority functions as integration infrastructure — reframes the entire assimilation debate away from culture or economics toward a structural feature of the receiving society.
• SEED: An essay pairing this finding with the inverse cases (e.g., Christian immigrants to Muslim-majority states) to argue that integration difficulty is a property of the match, not of the group.