The increase in hate crimes against Muslim immigrants after the 9/11 terrorist attacks led to the targeted community retreating from assimilation and becoming more traditional and more cohesive. That is the central conclusion of research by Eric Gould and Esteban Klor, which is forthcoming in the Economic Journal. What”s more, the rates of assimilation of Muslim immigrants was slower in parts of the United States where there was a more intensive backlash.

Analysing individual-level data from the Census and American Community Surveys between 1990 and 2010, the researchers find that after 9/11:

• There was an increase in the likelihood of Muslims marrying someone also from a Muslim country: the ”intra-marriage” rate rose by 6.4% and 7.3% for Muslim men and women respectively.

• The higher rate of intra-marriage came at the expense of marrying someone outside the ethnic group, rather than a general increase in the marriage rate.

• There was an increase in the number of children in Muslim households: by 5.7% and 4.5% for males and females respectively.

• There was a fall of 7.6% in the labour force participation of Muslim women.

• Muslim immigrants had lower proficiency in speaking English.

The authors comment:

”Our findings raise the possibility that terror groups may intentionally induce a backlash on persons of a similar ethnic origin in the targeted country, in order to decrease their rate of assimilation.”

”As a consequence, terror attacks against Western targets may have a long-term political and socio-economic impact, by creating a more insular and disconnected Muslim community in this generation and also the next.”

The study starts with the question of whether the terror attacks of 9/11 by radical Islamic groups induced a backlash against the Muslim community as a whole, raising their costs of assimilation. Evidence of a backlash is supported by FBI data on hate crimes against Muslims, which went from 28 reported incidents in 2000 to 481 in 2001.

The researchers then examine whether this backlash slowed the rate of assimilation by making use of variation across states in the number of hate crimes against Muslims in the wake of the 9/11 attacks. They show that the attacks induced a backlash that made the Muslim community in America more traditional in terms of marrying within the community, producing more children and having lower rates of female participation in the labour force.

For example, Figure 3 shows that changes in the state-level intra-marriage rate between 2000 and 2010 are correlated with the state-level changes in Muslim hate crimes per capita. For both men and women, there is a statistically significant positive relationship, showing that the assimilation rate of Muslim immigrants was indeed slower in places that experienced a more intensive backlash.

The results are not due to pre-existing trends in the assimilation outcomes of Muslim immigrants across states, and they are robust to inclusion or exclusion in the analysis of a wide array of personal and state-level characteristics. In particular, the study shows that Muslim immigrants were reacting specifically to hate crimes against Muslims, after controlling for the level of hate crimes against other groups.

Although the analysis uses data from the United States, the results are highly relevant for Europe for several reasons:

• First, the 9/11 attacks in the United States produced a backlash against Muslims in several countries throughout Europe.

• Second, there were subsequent attacks by Al Qaeda on major European cities after 9/11 – Madrid in 2004 and London in 2005 – which may have induced a further backlash.

• Third, Muslim immigrants in Europe tend to be less assimilated than other immigrant groups, and were so even before the 9/11 attacks.

The assimilation of Muslim immigrants is a much larger public issue in Europe than in the United States. This is probably because of the larger scale of the immigration wave and perhaps a result of the lower education levels of Muslims who migrated to Europe compared with those in the United States. The authors conclude:

”Our findings shed new light on our understanding of the increasing use of terror attacks on Western countries, with the concurrent rise in social and political tensions surrounding the assimilation of Muslim immigrants in Europe and the United States.”

”The Long-run Effect of 9/11: Terrorism, Backlash, and the Assimilation of Muslim Immigrants in the West” by Eric Gould and Esteban Klor is forthcoming in the Economic Journal. The authors are at the Hebrew University of Jerusalem.

Esteban Klor


Eric Gould

+1-301-767-6101 | eric.gould@huji.ac.il