New Dynamics of Population Diversity

New dynamics of population diversity. We will build on the PSC’s strengths in demography and the social study of race and ethnicity, plus Penn’s targeted institutional investment, to advance work on a central issue of the 21st Century: the relationship between health and inequality.

Population composition. The composition of national populations and their diversity is governed by mechanisms of exchange: the physical movement of persons between populations; but also the dynamics of classification and identity, by the state, by science, by social structure, and by persons themselves.

Migration. As the immigrant population grows, U.S fertility patterns will be increasingly determined by their behavior, but there is a lack of understanding of the interaction between immigration and fertility timing. Standard demographic techniques assume the two components are disconnected. However, migration can significantly distort the age-pattern of childbearing hence overestimate period levels of immigrant fertility. This has implications for the future size, age, and ethno-racial structure of the U.S. Parrado (PI, R01 HD075560) leads research that is measuring the contribution of immigrants; by racial/ethnic categories and national-origin, to U.S. fertility; and using tempo-adjusted fertility measures to make new projections of the U.S. population through 2050. Migration induces a related problem with respect to mortality, where many host countries have observed lower rates among immigrants than among natives, the lower socioeconomic status of the latter notwithstanding. Is this a result of the experience of migrants in the host country, of selection into the migration scheme, of selectivity in who remains in the host country and who returns home or migrates elsewhere, and/or are our data sources adequate for a by-definition mobile population? High quality French longitudinal social security data with mortality follow-up beyond France are being used to answer these questions (R01 HD079475 [PI, Guillot; co-I, Elo]). The ability to construct vital rates for accurately defined and well-measured national populations and sub-populations requires methods for studying transnational populations. Pilot support from R24 HD044964 and P30 AG012836 has led to pending application R21 HD095450 (MPIs Elo and Research Affiliate A Bawah, co-I, Behrman) for innovative survey work on what it really takes to link a U.S. population—Ghanaian immigrants to the U.S.—to their roots in the population of Ghana. Who left, and why? To whom should they be compared? How do sampling schemes adjust for the fact that some migrants have strong ties and others have weak ties; that some migration is individual and/or progressive within families; and that other migration is abrupt, with families moving all at once? These complementary projects benefit from the PSC as host for postdoctoral research fellows from varied disciplines and from International Partnerships with INED in France and RIPS in Ghana.

Race and ethnic identity. Roberts, whose 2011 book Fatal Invention pointed out that race is not a biological phenomenon freighted with political implications, but a political invention masquerading as a biological category, is the co-author of a 2016 Science article on “Taking race out of human genetics.” Phylogenetic and population genetic methods do not support classifications of race based on standard phenotypes. There are consequences for human health. Hemoglobinopathies can be misdiagnosed as long as sickle cell anemia is categorized as a "Black" disease, and conversely for cystic fibrosis, a "White" disease.  “Scientific journals and professional societies should encourage use of terms like ‘ancestry’ or ‘population’ to describe human groupings in genetic studies... It is preferable to refer to geographic ancestry, culture, socioeconomic status, and language … to untangle the complicated relationship between humans, their evolutionary history, and their health." Moreover, races are not fixed even in a demographic sense. Zuberi (in “El estudio de raza: la transición demográfica racial en América Latina,” 2015) notes strong recent increases in the number of “black” people in the Americas, increases that cannot be explained by migration or natural increase. It is change in self-identification associated with the Movimiento Negro in L America and is one of the biggest demographic transitions of contemporary times. With F. Griffith (Denison), in Int’l Handbook of Dem of Race and Ethnicity (2015), he reviews the history of racial and ethnic classification in S Africa. Classifications are dynamic. They evolved with the needs of colonial administrators and became embedded in a system of racial stratification that has furnished the “objective” grist for “scientific” explanations of group differences, and which endures post-Apartheid in its influence on personal identities. Charles and colleagues (Soc Race Ethn, 2015) use Add Health data to show that “inconsistency” in adolescent racial identity is not consequential with respect to emotional well-being, and use of a “White” identity might be somewhat beneficial. But the latter is not an individual choice and, in the U.S., is still accorded by others. In Beyond Expectations (2017), Imoagene shows that 2nd-generation Nigerian adults in the U.S. and Britain have an alternative notion of "black" identity that differs from African American and Black Caribbean notions of "black." The Nigerians define themselves in complicated ways that balance racial status, a diasporic Nigerian ethnicity, a pan-African identity, and identification with fellow immigrants. The Workshop in Race, Ethnicity and Immigration is a forum for developing similar work at the PSC, including linkages to migration, as in Flippen’s (City & Comm, 2016) distinctions between racial vs. ethnic, and residential vs. schooling, segregation as African-Americans move toward the Sunbelt and international immigration gives rise to more ethno-racial identities.

Health and inequality. The PSC brings together social scientists and health services researchers with a strong interest in how the core paradigms of the population sciences can be used to understand the social bases of health differentials, especially health outcomes as functions not just of socially distinguished individual characteristics, but of the way in which institutions, communities, and societies are organized. Work of this nature has taken on increased importance as economic and social inequality have increased within the U.S., along with increasing health disparities, which in general exceed those found in other nations. In the new SAS Strategic Plan, “Diversity, Inequality, and Human Well-Being” is the first among four areas that represent “the most compelling and far-reaching opportunities for SAS to integrate important and rapidly emerging areas of knowledge and inquiry.” Led by Parrado (with Krueger, MacDonald, and Smith) a proposal was developed and accepted to establish (via new hires) a Cluster in Health and Inequality, drawing on multiple disciplines, and centered at the PSC. The Cluster workshop will coordinate activity within the PSC and will help meld existing expertise and research agendas with those of new faculty to be hired under the initiative.

First cluster hires. Atal is a health economist who has written for the Inter-American Development Bank on gender and ethnic inequality in L America (IDB WPS No. 109). With Aiken, Behrman, and Smith, he is developing health-related projects in Chile via the International Partnership with Centro UC Encuestas y Estudios Longitudinales. Boen is a sociologist whose research focuses on the social determinants of population health inequality. She uses biomarkers of physiological functioning and cellular aging to understand how macro-level social inequality “gets under the skin” to produce health disparities from birth through late life. She has examined how disparities in socioeconomic conditions contribute to population health inequality (non-whites get less of a return on SES [Soc Sci Med, 2016]) and, with colleagues at UNC, how access to social relationships and exposure to relationship strain contribute to disparities in health and disease risk (PNAS, 2016). Hoke is a biological anthropologist. Her first-authored paper with T McDade (Northwestern) on biosocial inheritance (Ann Anthro Practice, 2014) maps out how early-life environments arise at the conjunction of intergenerational processes (epigenetics, immune function, growth and development) and current political-economic contexts (social and economic hierarchy, govt. programs).

Expertise: Demography. Ríos-Rull is a senior macroeconomist who returned to Penn to work more on demography at the PSC. In Demog (2014) he has developed a new methodology to compute differences in the expected longevity of individuals who have different SES characteristics at a given age to address two problems associated with the use of life expectancies: that many SES characteristics evolve over time, and that there are time trends in mortality. Decomposing differences in longevity into a fraction due to differences in self-perceived initial health, changes in health, and differences in mortality among groups with different SES characteristics shows that the most important component is the advantage that various socioeconomic groups have in preserving health. An implication is that SES differences in mortality are likely to widen. Elo has been an international leader in the demography of health and inequality, including via ongoing research with Preston and others on changes and differentials in life expectancy, plus her work on migration and health. A paper in Soc Sci Med: Pop Health (2016) follows the Finnish population of Karelia who were forced to migrate during WWII, and finds no long-term health consequences relative to comparable non-forced migrants. Why? Likely because they were well integrated into post-war Finnish society.

Expertise: Population genetics. Schurr is an anthropologist and molecular biologist and Director of the North American Regional Center of the Genographic Project, which is mapping the human population among haplogroups. In a 2016 paper in Circulation: Cardiovascular Genetics, he and his colleagues consider the extent to which differences in mitochondrial bioenergetics and mtDNA damage associated with maternal ancestry may contribute to endothelial dysfunction and vascular disease.

Expertise: Health services research. The PSC has a strong set of health service researches looking at health and inequality at the population level. In Healthcare (2016), Polsky and colleagues link insurance claims data on emergency room use to ~5000 census tracts, and show that net of substantial geographic heterogeneity, race, ethnicity and poverty are associated with higher use of emergency departments, but not in suburban and rural regions. Under R01 AG041099, McHugh (PI; Aiken, Smith, co-I) will examine over a large, representative multi-state set of minority-serving hospitals and patients, whether changes in practice environments have reduced disparities in health outcomes based on race or ethnicity. Mandell, in Autism (2017), shows how minority status among children with developmental disabilities puts them at even greater risk of social isolation in schools.