The size of the combined Mexico- and U.S.-based sample is typically based on 700 to 1,000 interviews per year. The survey usually targets household heads, but it also interviews other adults (ages 15-65) in the household. Since a census is essentially taken within the community, there is no sampling error and hence there are no sample weights. Refusal rates tend to be less than 10 percent.
The focus of the interviews and, hence, the survey questionnaire changes every year. This allows the MMFRP to address the most recent developments, such as the impact of the U.S. recession on migration or the deterrent effect of border enforcement. Although the annual themes differ, the surveys consistently include information similar to the MMP on social, demographic, and economic variables. In addition, it asks about intended and actual migration, networks, remittances, perceptions of border enforcement and other immigration laws, and legal status. For the undocumented, it asks about how the border crossing was made, coyote usage and price, and any abuse or mistreatment, if applicable (for first and last trip, as in the MMP). The MMFRP also asks migrants why they return to Mexico or why they stay in the United States. Other information varies by survey year. At one time or another, questions have included welfare program usage in Mexico, race relations and ethnic identity, politics and civic participation, religion, future plans, and more.
The MMFRP data and documentation have recently been made available on the CCIS website. Researchers who participate in the MMFRP program in a given year write up their results as chapters in a book that focuses on that year’s survey theme. (See, e.g., Cornelius et al., 2010, which examines how the U.S. economic recession that began in 2007 has affected flows of Mexican immigrants to and from the United States.30)