Our work was possible thanks to the support of the William and Flora T. Hewlett Foundation, the Mexican Secretariat of Foreign Affairs, the John D. and Catherine T. MacArthur Foundation, and each of our institutions. We are a nongovernmental group. Our views and recommendations are the sole responsibility of the group of experts. However, we believe policy-relevant work cannot be developed by academics alone. We have benefited from the input of the Mexican Secretariat of Foreign Affairs, and we have also discussed our progress with officials from each country: in the United States, the Department of Homeland Security, the U.S. Census Bureau, the State Department, and the U.S. Congress; and in Mexico, the National Institute of Migration, the National Population Council, the Mexican Social Security Institute, and the Social Development Secretariat. A particular thank you goes to Laura Pedraza for her excellent editorial assistance. We are also grateful to various academics and policy experts from both countries who have discussed our findings and made constructive suggestions. Our views, nevertheless, remain entirely our own.