Populations, Volume 1, Issue 1 (March 2025) – 5 articles

I rely on the key concepts of diffusion and percolation to characterize the sequential but overlapping phases of the spread of infection through entire populations during the first year of the COVID-19 pandemic. Data from Los Angeles County demonstrate an extended initial diffusion phase propelled by radial geographic spread, followed by percolation within hotspots fueled by the presence of multigenerational households. Data from New York City, by contrast, reveal rapid initial diffusion along a unique, extensive subway network. Subsequent percolation within multiple hotspots, similarly powered by a high density of multigenerational households, exerted a positive feedback effect that further enhanced diffusion. Data from Florida counties support the generality of the phenomenon of viral transmission from more mobile, younger individuals to less mobile, older individuals. Data from the South Brooklyn hotspot reveal the limitations of some forms of government regulation in controlling mobility patterns that were critical to the continued percolation of the viral infection. Data from a COVID-19 outbreak at the University of Wisconsin—Madison demonstrate the critical role of a cluster of off-campus bars as an attractor for the continued percolation of infection. The evidence also demonstrates the efficacy of quarantine as a control strategy when the hotspot is contained and well identified. Full article

This study uses data from the 2006–2012 Health and Retirement Study (HRS) genetic sample (N = 11,667) to explore the “immigrant health paradox” from a novel perspective by examining the nativity differences in genetic predisposition to health-related outcomes. Polygenic indices (PGIs) were used to evaluate whether older non-Hispanic white foreign-born individuals have genotypes that predispose them to better health profiles compared to their U.S.-born counterparts. The results show an immigrant advantage with respect to genetic predisposition to cognitive function, BMI, and smoking frequency. There are no significant differences in genetic predisposition to height, smoking initiation, and depression. Including respective PGIs in multinomial regression models partially explains an immigrant advantage with respect to cognitive function and obesity. The findings are consistent with the “healthy immigrant effect” or selective migration of individuals with a favorable genetic predisposition to health as one of the explanations of the immigrant health paradox. Full article

For the United States, detailed estimates of the number of resident migrants and the rates of migrant arrival are valuable for understanding population dynamics and for determining the impact of economic and political changes that influence migration. The goal of this analysis was to derive estimates of the U.S. foreign-born population and how this population has changed in recent years, as well as estimates of recent and historical immigration volumes. Using data from large population surveys (the 2000 U.S. decennial census and 2001–2019 American Community Survey (ACS)), a Bayesian evidence synthesis was conducted to pool survey data across years while accounting for various biases and logical constraints that apply to these data. This analysis produced highly disaggregated estimates of the foreign-born population residing in the United States over the period 2000–2019, as well as estimates of immigration volume for 1950–2019. These population estimates demonstrated high in- and out-of-sample predictive performance, with substantially greater precision than that for raw survey estimates. Estimated immigration flows tracked other available time series, although with higher precision and with the potential to include undocumented immigration not represented in other immigration data. This study documents immigration from 100 countries of origin into the United States and demonstrates how the results of repeated cross-sectional population surveys can be used to infer migration dynamics that are difficult to measure directly. Full article