Professor Gratton received his doctorate in 1980 from Boston University and worked as a postdoctoral fellow at Case Western Reserve University from 1981 to 1983. His initial research, summarized in Old Age and the Search for Security, focused on social security, retirement and the circumstances of the American elderly.  Although he continues this interest, his principal emphasis is now in immigration and migration, particularly among Hispanics. He worked on these subjects while a Fulbright fellow in Spain (1996) and in Ecuador (2002).  In 2004 and 2005, as a fellow at the Russell Sage Foundation in New York, he wrote on the issue of assimilation among immigrant-origin persons, tracing generational fortunes from 1850 to the present.

His publications on ethnicity and immigration in the United States, Ecuador and Europe include articles in the Journal of American Ethnic History, Professional Geographer, The Journal of Ethnic and Migration Studies, Historical Statistics of the United States, and the Journal of Interdisciplinary History.  During 1996–97, Dr. Gratton was a National Institutes of Health (NIH) fellow at the University of Texas at Austin, developing a new series of representative samples of Hispanic and other immigrant-origin groups from the United States Censuses.  This project led in 1999 to a two-year research grant from the National Institute of Child Health and Human Development to study assimilation trajectories in Mexican-American families.  With support from the National Institute on Aging in 2003-2007, he extended this research to historical analysis of elderly immigrants.  He is now engaged in writing a sociopolitical account of 400 years of immigration to what is now the United States, a broad consideration of demography, popular reaction, and public policy.

Professor Gratton has received funding for teaching from the Department of Education through four consecutive Teaching American History Grants. His teaching and research intersts include ethnicity and immigration and labor, economic and social welfare history. His teaching looks closely at gender questions within migrant groups and at ethnic conflict as an endemic characteristic of human societies.