Islamic terrorism, backlash, and the assimilation of Muslim immigrants in western countries

Eric Gould, Esteban Klor 16 December 2015



Hate crimes against Muslims flared up in a number of western countries immediately after the terror attacks in Paris. In the following weeks, they soared to alarming numbers in France, as expected, but also in other European countries, especially in the UK. The Atlantic Ocean was not able to stop the backlash against Muslims, as hate crimes were also committed in Canada and the US.

In the meantime, western governments find themselves in the difficult position of trying to track down and stop home-grown Islamic terror cells, while also assuring law-abiding Muslim citizens that they are welcomed and appreciated. Beyond their goal of providing a safe environment to every citizen, western governments are concerned that the prevailing animosity against Muslims will make them feel isolated and, ultimately, lead to less assimilation and perhaps the radicalisation of some (Baldwin 2015).

The effect of terror attacks on Muslim assimilation: New evidence

In Gould and Klor (2012), we investigate whether the assimilation process of Muslims is affected by a backlash in the aftermath of terror attacks by a radical Islamic group. In particular, we examine how the 9/11 attacks affected the assimilation outcomes of the Muslim community within the US. Our paper is the first systematic empirical analysis of whether the backlash against Muslim Americans after 9/11 affected their rate of assimilation in the US. The lack of research on this subject is surprising given the increasing social and political tensions surrounding the assimilation of a large influx of Muslim immigrants to west European countries and North America, and a concurrent increase in the use of large-scale terror attacks on western cities.

The most related literature on this subject has been conducted by historians, sociologists, journalists, and Islamic scholars, who claim that Muslims and their communities in the US underwent substantial changes after the 9/11 attacks (Abdo 2006, Barrett 2008, Bakalian and Bozorgmehr 2009). These studies argue that American Muslims, who felt under attack by the government, the general public, and the media in the aftermath of 9/11, sought refuge in their religion and community to withstand the backlash. According to these authors, the 9/11 attacks spurred a renewed sense of solidarity among Muslims and a religious revival in the face of widespread criticism of Islam.

But the existing literature suffers from several shortcomings. The empirical evidence is based on a small number of selected interviews. Individuals who agree to be interviewed may not have opinions that reflect the average person’s experience, and an individual’s thoughts and opinions may not match their actions. In addition, the existing literature does not attempt to establish a causal connection between the backlash and assimilation, and therefore cannot determine whether the changes in the Muslim community after 9/11 were due to the attacks themselves or were part of a pre-existing trend in their assimilation patterns.

Evidence for a backlash after 9/11 is supported by the data on hate crimes against Muslims. Data on anti-Muslim hate crimes collected by the FBI show a dramatic increase in the wake of the 9/11 attacks. With only four months remaining in the calendar year after the incident, the reported total number of hate crimes against Muslims increased 1,600% from 2000 to 2001. This sudden jump is displayed in Figure 1, which also shows that the number of hate crimes against Muslims decreased after the surge following the 9/11 attacks, but settled down to a yearly mean of 139.5 incidents after 2001 compared with 23.3 prior to 2001.

Figure 1. Hate crimes against Muslims in the US

Source: FBI Uniform Crime Reporting (UCR) Program.

Our analysis uses the data on hate crimes as a proxy for the extent of the backlash against Muslims, and merges this information with data on the characteristics and assimilation patterns of immigrants from Muslim countries over time. These data come from the US Census in 1990 and 2000, as well as the American Community Surveys (ACS) for 2007-2010. Using the Census and ACS data, we construct several standard measures of assimilation for each Muslim immigrant in the sample. Our first measure is whether the person is ‘intra-married’ in the sense of being married to someone whose ancestry is from a Muslim country. This measure is widely used to capture the strength of one’s ethnic identity and level of assimilation (Bisin and Verdier 2000, Bisin et al. 2004). Our other measures of assimilation include the respondent’s fertility, labour force participation, and proficiency in English.

In order to control for the national trends in the assimilation patterns of Muslim immigrants, which may be correlated with the upward trend in anti-Muslim hate crimes, our empirical strategy exploits variation across states in the extent of the backlash, and tests for whether changes in the assimilation patterns of Muslims across states since 2001 are associated with the size of the local backlash.

Figure 2 presents a first look at whether 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, suggesting that the assimilation rate of Muslim immigrants was indeed slower in places that experienced a more intensive backlash.

Figure 2. State analysis of intra-marriage, 2000-2010

Notes: Female Slope = 1.177 (tstat=3.56); Male Slope = 0.764 (tstat=2.31). Regressions are weighted by state sample size, represented by the size of each circle.

Main findings

Looking at all of the outcomes of interest, our results show that Muslim immigrants living in states that experienced the sharpest increase in hate crimes after 9/11 also exhibit:

  • Greater chances of ‘intra-marriage’ (marrying someone who also originates from a Muslim country);
  • Higher fertility;
  • Lower female labour force participation; and
  • Lower English proficiency.

The higher rate of intra-marriage comes at the expense of marrying outside of the ethnic group, rather than a general increase in the marriage rate. All of these patterns are consistent with a less-assimilated outcome, since Muslim countries are characterised by very low rates of female labour force participation and high fertility rates compared to natives in the US.

Overall, our findings show that the 9/11 attacks induced a backlash that made the Muslim community in America more traditional and less assimilated. In order to attribute a causal interpretation to our results, it is important to note that the state-level increase in hate crimes against Muslims after the 9/11 attacks was not correlated with the pre-existing state-level trend in any of the assimilation outcomes, or with the characteristics of Muslim immigrants living in the state prior to the 9/11 attacks. In addition, the results are robust to the inclusion or exclusion of a rich set of personal and state-level characteristics, including state-level hate crimes against blacks, Jews, and homosexuals. These findings support our identifying assumption that variation in the extent of the backlash across states can be considered exogenous.

Moreover, a placebo analysis shows no effect of hate crimes on the marriage decisions of older Muslim immigrants who largely already made their marriage decisions before the 9/11 attacks, and by showing that no other immigrant group exhibited a slower rate of assimilation in response to hate crimes against Muslims. These findings lend even more support for a causal interpretation for our findings that the 9/11 attacks increased the ethnic identity of the Muslim community in the US.

Concluding remarks

Our study is the first systematic empirical analysis of how the Muslim community in the US reacted to the 9/11 attacks. Our findings present the first evidence that the backlash against Muslims slowed their rate of assimilation, as reflected by higher rates of intra-marriage and fertility, and lower rates of female labour force participation and English proficiency. In this manner, our findings suggest that terror attacks against western targets may have a long-term political and socio-economic impact, by creating a less assimilated, and perhaps more isolated Muslim community in this generation and possibly the next.

The idea that terror groups instigate a backlash is not new in the theoretical literature on political conflict (Rosendorff and Sandler 2004, Bueno de Mesquita and Dickson 2007, Baliga and Sjöström 2012). However, this literature focuses on the backlash against the country or territory where the perpetrators reside. In the context of 9/11, this is consistent with the US attacking Afghanistan.

Our findings raise the possibility that terror groups may also intentionally induce a backlash on persons of a similar ethnic origin in the targeted country, in order to decrease their rate of assimilation. This strategy is consistent with the writings of some of the most prominent Jihadist leaders. Abu Musab al-Suri, for example, repeatedly calls for independent terror attacks against western targets. He hopes that these attacks, and the backlash they generate, will inspire other Muslims living in the west to radicalise.


Abdo, G (2006), Mecca and Main Street: Muslim Life in America after 9/11, New York: Oxford University Press.

Baldwin, R (2015), “Past Vox columns on terrorism and terrorists”,, 14 November.

Bakalian, A P and M Bozorgmehr (2009), Backlash 9/11: Middle Eastern and Muslim Americans Respond, Berkeley: University of California Press.

Baliga, S and T Sjöström (2012), ‘The Strategy of Manipulating Conflict,’ American Economic Review, 106 (2), 2897-2922.

Barrett, P M (2008), American Islam: The Struggle for the Soul of a Religion, New York: Picador.

Bisin, A, G Topa and T Verdier (2004), ‘Religious Intermarriage and Socialization in the United States,’ The Journal of Political Economy, 112 (3), 615-664.

Bisin, A and T Verdier (2000). ‘Beyond the Melting Pot: Cultural Transmission, Marriage and the Evolution of Ethnic and Religious Traits,’ The Quarterly Journal of Economics, 115 (4), 955-988.

Bueno de Mesquita, E and E S Dickson (2007), ‘The Propaganda of the Deed: Terrorism, Counterterrorism, and Mobilization.’ American Journal of Political Science, 51(2), 364–381.

Gould, E D and E F Klor (2012), ‘The Long-Run Effect of 9/11: Terrorism, Backlash, and the Assimilation of Muslim Immigrants in the West,’ CEPR DP No. 8797.

Rosendorff, B P and T Sandler (2004). ‘Too Much of a Good Thing? The Proactive Response Dilemma,’ The Journal of Conflict Resolution, 48 (4), 657-671.



Topics:  Frontiers of economic research Politics and economics

Tags:  terrorism, Muslim assimilation, 9/11 attacks

Professor of Economics, Hebrew University; Research Fellow, IZA; Fellow at CReAM, University College London; and CEPR Research Fellow

Senior Lecturer, Department of Economics, Hebrew University of Jerusalem