In 2007, the Pew Research Center conducted what is believed to be the first-ever national telephone survey of a probability sample of Muslim Americans, a rare, dispersed, and highly diverse population. The study examined the political and social values, religious beliefs and practices, and life experiences of Muslims living in the U.S. today. The survey also contrasts the views of the Muslim population as a whole with those of the U.S. general population, and with the attitudes of Muslims all around the world, including Western Europe. Finally, findings from the survey make important contributions to the debate over the total size of the Muslim American population.
- Data File
- Cases: 1,050
Weight Variable: WEIGHT
- Data Collection
- Date Collected: January 24-April 30, 2007
- Funded By
- The Pew Charitable Trusts
- Collection Procedures
- Telephone interviews conducted in English, Arabic, Farsi, and Urdu, under the direction of Schulman, Ronca & Bucuvalas, Inc.
- Sampling Procedures
- "Pew’s sample design attempted to address the low incidence and dispersion of the population by employing two separate sampling frames:
"1. An RDD frame divided into five strata, four of which were based on the estimated density of the Muslim population in each county of the United States as determined through an analysis of Pew’s database of more than 125,000 survey respondents and U.S. Census Bureau data on ethnicity and language. To increase the efficiency of the calling, the lowest density stratum – estimated to be home to approximately 5%-21% of U.S. Muslims – was excluded. A disproportionate sampling strategy was employed to maximize the effective sample size from the other three geographic strata (total N=354). The fifth stratum was a commercial list of approximately 450,000 households believed to
include Muslims, based on an analysis of first and last names common among Muslims. This stratum yielded completed interviews with 533 respondents.
"2. A sample of previously identified Muslim households drawn from Pew’s interview database and other RDD surveys conducted in recent years. Recontacting these respondents from prior surveys yielded 163 completed interviews for this study. The strength of this research design was that it yielded a probability sample. That is, each adult in the U.S. had a known probability of being included in the study. The fact that some persons had a greater chance of being included than others (e.g., because they live in places where there are more Muslims) is taken into account in the statistical adjustment described below (section 4). One limitation of this design is that the samples were of landline telephone numbers. Thus, Muslims living in homes with no telephone or who only have a cell phone had no chance of being sampled for the study. To account for this, we used the most recent government data on telephone service to adjust our estimate of the total size of the Muslim population.
"RDD Geographic Strata
Pew Research Center surveys conducted in English typically encounter a little more than four Muslim respondents per thousand interviews, an unweighted incidence rate of 0.42%. This rate has varied somewhat over the past seven years, ranging from a high of 0.57% thus far in 2007 to 0.33% in 2005. The rate is also very similar to that encountered by other national surveys (for instance, see Tom Smith’s “The Muslim Population of the United States: The Methodology of Estimates” in Public Opinion Quarterly, Fall 2002). This low incidence means that the costs of building an RDD sample of Muslim Americans by screening a general public sample are prohibitive. Accordingly, it was necessary to develop alternative approaches that would allow for estimation of the probabilities of selection but increase the yield from screening.
"An analysis of the geographic distribution of the Muslim population was undertaken, using several different sources of data. A key resource was the Pew Research Center database of more than 125,000 telephone interviews conducted between 2000 and 2006 (when planning for this project was completed); it was used to estimate the density of Muslims in each U.S. county. Another resource was data from large government surveys. The U.S. Census Bureau does not collect information about religion, but it does include measures of ancestry, nationality for immigrants, and languages spoken. These measures were used to analyze the geographic distribution of adults who are from (or whose parents are from) countries with significant or majority Muslim populations, or who speak languages commonly spoken by Muslims. This yielded additional county-level estimates of the density of Muslims.
"These measures were highly correlated and were used to sort counties into four different groups based on the
estimated incidence of Muslims in each county. We refer to these mutually exclusive groups as the geographic strata. The lowest density stratum accounts for 5% of all Muslim interviews conducted by Pew over the past seven years; the second lowest accounts for 29% of Muslim interviews; the medium density stratum accounts for 51%; and the highest density stratum accounts for 15%.
"Drawing on the analysis of previous Pew surveys, Census Bureau data, and the results of a pilot test, an optimal sampling allocation plan was developed for the RDD geographic strata. The sampling plan called for conducting roughly 33% of all RDD screening interviews in the lower density stratum, 53% of all RDD screening interviews in the medium density stratum, and 14% in the high density stratum. In total, 57,549 screening interviews were completed, and the distribution of completed interviews was nearly identical to the original allocation plan.
"The lowest density stratum, which included 5% of all U.S. Muslims in Pew surveys (and up to 21% as based on estimates derived from U.S. Census Bureau data), also includes 47% of the total U.S. population. As a practical matter, the analysis of the Pew database indicated that 25,000 screening interviews would have to be conducted in this stratum to yield an estimated 10 Muslim respondents. In order to put the study’s resources to the most efficient use, this stratum
was excluded from the geographic strata of the RDD sample design, although persons living in these counties were still covered by the list stratum and recontact frame.
"The danger in excluding this very low density stratum is that the individuals excluded may be significantly different from the rest of the population. To assess this potential bias, interviews from the list stratum and the recontact frame were used to compare Muslims in the lowest density stratum (the excluded area) with those living in the higher density areas. Muslims in the excluded area are more satisfied with their financial situation, somewhat more tolerant of homosexuality, less likely to say that it has become harder to be a Muslim in the U.S. since 9/11, and somewhat more secular in their approach to religion. However, Muslims living in the lowest density stratum comprise a relatively small proportion of all U.S. Muslims, and these differences are not so large that their exclusion would be expected to significantly affect the overall estimates.
"RDD List Stratum
Within the RDD frame of U.S. telephone numbers, we used a targeted, commercial list to identify roughly 450,000 numbers that had a relatively high probability of belonging to a household with a Muslim adult. We defined this list as its own stratum within the RDD frame. This list was constructed from a commercial database of households where someone in the household has a name commonly found among Muslims. The list was prepared by Experian, a
commercial credit and market research firm that collects and summarizes data from approximately 110,000,000 U.S. households. The analysis of names was conducted by Ethnic Technologies, LLC, a firm specializing in multicultural marketing lists, ethnic identification software, and ethnic data appending services. According to Experian, the analysis uses computer rules for first names, surnames, surname prefixes and suffixes, and geographic criteria in a specific order to identify an individual’s ethnicity, religion and language preference.
"In late 2006, Pew purchased Experian’s database of more than 450,000 households thought to include Muslims. This list consists of contact information, including telephone numbers. A test of the list, combined with the results of the screening interviews conducted in the course of the main survey, found that the Experian list was a highly efficient source for contacting Muslims; roughly one-third of households screened from the Experian list included an adult Muslim. The list does not, however, by itself constitute a representative sample of American Muslims. Muslims in the Experian database earn higher incomes, are better educated, are more likely to be of South Asian descent and are much less likely to be African American compared with Muslim Americans as a whole.
"By combining the Experian list with the RDD frame, however, the list can be used as one component of a probability sample. All telephone numbers drawn for the geographic strata of the RDD frame were compared to the entire Experian list of numbers. Any numbers that appeared in both the RDD geographic sample and the Experian list were removed from the former, and were available to be sampled only as part of the list stratum. This method makes it possible to determine the probability that any given Muslim has of being sampled, regardless of whether he or she is included in the Experian list. It also permits estimation of the proportion of all Muslims in the U.S. who are covered by the Experian list, which in turn makes it possible, in the final analysis, to give cases from the Experian sample an appropriate weight. More details on the statistical procedures used to incorporate the list into the overall sample are provided below.
In addition to contacting and interviewing a fresh sample of Muslim Americans, the phone numbers of all Muslim households from previous Pew surveys conducted between 2000 and 2006 were called. Adults in these households were screened and interviewed in the same manner used for the RDD frame. No attempt was made to re-interview the same respondent from earlier surveys. Pew’s survey partners, Princeton Survey Research Associates International (PSRAI) and SRBI, also provided lists of Muslims interviewed in the course of other national surveys conducted in recent years. In total, the recontact frame consisted of phone numbers for 796 Muslims interviewed in recent national surveys; 309 of these households were successfully screened, resulting in 163 completed interviews with Muslims.
"The greatest strengths of the recontact frame are that it consists entirely of respondents originally interviewed in the course of nationally representative surveys based on probability samples and that it includes respondents who live in the geographic stratum that was excluded from the RDD sample. However, there also are certain potential biases of the recontact frame. Perhaps most obviously, since all of the previous surveys from which the recontact frame was drawn were conducted either entirely in English, or in English and Spanish, Muslims who do not speak English (or Spanish) are likely absent in the recontact frame. Another potential source of bias relates to the length of time between when respondents were first interviewed and the current field period; respondents still residing in the same household in 2007 as in an earlier year may represent a more established, less mobile population compared with those from households that could not be recontacted.
"Analysis of the survey results suggests that there are some differences between Muslims in the recontact frame and those in the RDD frame. Not surprisingly, Muslims from the recontact frame are more likely than others to own their home. They express somewhat higher levels of satisfaction with their own financial situations, report lower levels of mosque attendance and religious salience, and express somewhat higher levels of dissatisfaction with the direction of the country. These differences, however, are not sufficiently large so as to be able to substantially affect the survey’s estimates."
- Principal Investigators
- The Pew Research Center for the People & the Press and the Pew Forum on Religion & Public Life, with additional advice and assistance from staff in the Pew Hispanic Center and the Pew Global Attitudes Project.
- Related Publications
- Muslim Americans: Middle Class and Mostly Mainstream http://pewsocialtrends.org/assets/pdf/muslim-americans.pdf