Genetic Selectivity in Migration: Polygenic Insights into Heterogeneous Outcomes of Domestic Migration in the US
Liu Y1,*
1Sociology Department, Princeton University, Princeton, NJ, USA
*Presenting author: Yuxin Liu
Corresponding author email: yl9858@princeton.edu
Short Abstract
What makes migrant outcomes so different? Migration studies often grapple with selection bias and unobserved confounders, such as education, socioeconomic status (SES), and health, which complicate the understanding of migration outcomes. This study leverages genetic data to address these challenges, utilizing polygenic scores (PGS) to examine the genetic selectivity of various types of internal migration in the United States. Employing data from AddHealth, the research investigates the genetic profiles of U.S. migrants, focusing on traits such as educational attainment, health, and behavioral traits. Beyond the aggregated-level picture, it specifically attends to the different genetic profiles and selectivity among various types of migrants, especially long-distance and short-distance migrants.
The study proceeds in three steps: (1) identifying heterogeneity among migrants, (2) comparing genetic profiles across different migration groups to assess the direction and magnitude of genetic selectivity, and (3) employing within-family designs to establish causal relationships between genetic traits and migration behaviors. Specifically, it explores whether long-distance migrants exhibit positive genetic selectivity (e.g., higher PGS for educational attainment and health) while short-distance, frequent movers display negative selectivity (e.g., higher PGS for risk-prone behaviors and lower SES).
By integrating genetic insights with sociological perspectives, this research aims to reconcile two competing theories of migration outcomes—one emphasizing the advantages of positively selected migrants and the other highlighting the challenges faced by disadvantaged movers. This study offers innovative methodological contributions and practical implications for addressing disparities among migrant populations in the U.S.
Theoretical Framework
Two competing models exist for the understanding of migration selectivity and outcomes. The first approach suggests that migration requires determination and resources and therefore is positively selected and leads to advantageous results (Chiswick, 1999; Feliciano, 2005; Abramitzky & Boustan, 2017; Aksoy & Poutvaara, 2021). The second approach, by contrast, argues that migration produces broken social ties and interrupted routines, thus bringing about negative consequences such as increased delinquency. The second approach also suggests that migration attracts risk-seeking people and those with disadvantaged socioeconomic status, especially among short-distance, frequent, and compelled movers (Garboden et al., 2017; Kogan et al., 2011; Sharkey & Sampson, 2010).
The two theories, in fact, are not mutually exclusive; they point in conflicting directions only because they are built on different sets of assumptions. The first positive model assumes that migrants are voluntarily choosing to relocate to achieve specific economic goals, and once they succeed their improved situation will yield better outcomes. This applies more effectively to long-distance migrants. On the other hand, the second approach attends to the fact that many migrants are less self-driven and more dependent on environmental constraints. Short-distance, more frequent migration is usually included in that interpretation. This study attempts to use empirical analysis to evaluate these two seemingly conflicting theories by disentangling the genetic profile of migrants and the migration outcomes.
Methods
This study will proceed in three main steps. First, migration groups that are both theoretically and empirically different in terms of migration behavior and outcomes are identified, including migration distance, migration intention, sending and receiving communities, gender, age, etc. Migration distance will be the most discussed category, where short-distance migrants are defined as those moving within the same neighborhood (5km radius) and long-distance migrants move further than 160km.
Second, I compare the PGI for educational attainment, behavioral traits, and health measures across different migration groups. These comparisons will include migrants versus non-migrants, as well as long-distance, less frequent migrants versus short-distance, more frequent migrants. This comprehensive analysis will provide a detailed and nuanced understanding of the genetic selectivity of migrants across diverse contexts.
Lastly, I will evaluate whether the genetic selectivity found in previous steps is indeed causally correlated with migration behavior by adopting a within-family design. By controlling for parents’ genotype, the randomly inherited genetic variants can serve as a natural experiment to address the identification issues of confounding and reverse causation (Davies et al., 2018). Mendelian imputation will be utilized to calculate the parents’ genotype when one of the parents’ data is missing (Young et al., 2022).
Hypothesis
- Long-distance migrants are genetically positively selected in terms of health, socioeconomic status, and behavioral traits, while short-distance, more frequent movers have negative genetic selectivity.
- Those with a higher genetic propensity to move long distances, regardless of their actual migration actions, also have a higher genetic propensity for better socioeconomic status and health.
- The positive and negative genetic profiles found in previous sections are causally related to long- and short-distance mobility behaviors.
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