Not Clearly Pro or Con to the question "Should the Government Allow Immigrants Who Are Here Illegally to Become US Citizens?"
"[E]stimates of the number counted in the census  provide a firm empirical basis for setting a lower bound on the total in the country as of 1980. The estimates presented in this paper, along with the results of other studies (Panel on Immigration Statistics, 1985), suggest that the undocumented Mexican population in 1980 was in the 1-2 million range, with the total number from all countries falling in the range of 2-4 million... Of the undocumented present and counted in 1980, 941,000 entered during 1975-1980; 576,000 entered during 1970-1974; and 540,000 entered before 1970... Finally, the estimates for 1980 show a high proportion of recent arrivals, and very few who entered the United States prior to 1960."
"A Count of the Uncountable: Estimates of Undocumented Aliens Counted in the 1980 United States Census," August, 1987
[Editor's Note: Dr. Passel confirmed his "Not Clearly Pro or Con" position in a Sep. 1, 2009 email to ProCon.org by stating: "This is the correct placement because the organization for which I work, Pew Hispanic Center, according to its mission statement '...is a nonpartisan research organization that seeks to improve understanding of the US Hispanic population and to chronicle Latinos' growing impact on the nation. The Center does not take positions on policy issues. It is a project of the Pew Research Center, a nonpartisan 'fact tank' in Washington, DC that provides information on the issues, attitudes and trends shaping America and the world...' I would also add that we do not do research evaluating policies."]
Experts Individuals with advanced degrees in fields relevant to immigration. Also top-level government officials (such as foreign leaders, US presidents, Founding Fathers, Supreme Court Justices, members of legislative bodies, cabinet members, military leaders, etc.) with positions relevant to immigration.
Involvement and Affiliations:
Senior Demographer, Pew Research Center, 2005 - present
Principal Research Associate, Urban Institute, Labor, Human Services and Population Center, 1989 - 2005
Selected, "Demographic Diamond," American Demographics magazine, 2004
Senior Statistician, US Bureau of the Census, Population Division, 1974 - 1989
Member, Social Security Advisory Board’s Technical Panel
Fellow, American Statistical Association
Fellow, American Association for the Advancement of Science
Former Member, Population Association of America
Former Member, Panels of National Academy of Sciences