The Impact of the Great Migration on Mortality of African Americans: Evidence from the Deep South.

The Great Migration—the early twentieth-century migration of Southern-born African Americans to locations with better social and economic opportunities—played a pivotal role in the lives of millions of individuals. At the onset of the Great Migration and as it was underway, there were suggestions that migration out of the South might be an important avenue for improving the health of African Americans (Wright, 1906; Myrdal, 1948), but also concerns about adverse health conditions in urban areas to which blacks were migrating (Bureau of the Census, 1918). To our knowledge, though, no research has evaluated the long-term impact of the Great Migration on health outcomes of migrating individuals. Our paper tackles this issue, focusing on mortality among African Americans born in the “Deep South” states of South Carolina, Georgia, Alabama, Mississippi, and Louisiana. Figure 1 gives a sense of magnitude and timing of African American migration out of the Deep South, providing out-migration rates from the Deep South by ages 40–49 for birth cohorts 1891 through 1955. Migration rates were approximately 20 percent for the earliest of these cohorts, and migration subsequently increased substantially; for each birth cohort 1914 through 1943, the migration rate was at least 40 percent. As we describe below, due to data availability, we study birth cohorts 1916 through 1932, which are among the high-migration cohorts. Figure 1 Proportion of African Americans Migrating out of the Deep South as of their 40s, Birth Cohorts 1891–1955 Economic historians refer to a variety of “push” and “pull” factors were at play in shaping the scale and timing of the Great Migration. To give a few examples, Collins (1997) and Carrington, Detragiache and Vishwanath (1996) emphasize increasing demand for labor in the North post World War I, which was in part the consequence of restrictions on foreign immigration; Alston and Ferrie (1993) discuss the breakdown of “paternalistic” labor practices due to the mechanization of cotton production; Lange, Olmstead, and Rhode (2008) assign a key role to damage to agriculture from the boll weevil; and Boustan (2010) demonstrates that county-level out-migration of African Americans from the South was influenced over time by variation in a variety of agricultural conditions. A key challenge for drawing credible inferences about the impact of this migration on mortality is that migrants are a select group; these individuals pay a possibly high cost—direct migration costs, and also often a loss of present-day economic security and diminished contact with community and family—in the hope that life will be better elsewhere. Migrants thus plausibly have relatively high aspirations and motivation, traits associated with human capital investment generally, including investments in health. As Norman, Boyle, and Rees (2005) note, at least since Farr (1864), scholars have understood that migrants may differ systematically from non-migrants in terms of characteristics related to health. Any effort to estimate the causal impact of the Great Migration on mortality must account for this issue.1 In our work below, we employ two research strategies for drawing inference about the impact of migration on mortality: Our first and most innovative strategy is to use the proximity of birthplace to railroads as an instrument for migration. Historians have emphasized the outsized role played by railroads in facilitating the Great Migration and shaping migratory pathways. For example, railroads appear to have contributed to a “vertical” pattern of much of the Great Migration. It seems that African Americans from the South often began travel from the nearest train stop, and then often settled near the terminus of the same rail lines. Such tendencies may have contributed to the migratory streams from the Carolinas to cities on the eastern seaboard (Washington D.C., Philadelphia and New York) via the Southern Railway and Pennsylvania Railroad, and from Mississippi to Chicago via the Illinois Central Railroad. Below we show that proximity of birthplace to a railroad is a powerful predictor of migration for Southern-born African Americans. Under the assumption that being born in a railroad town otherwise has no impact on late-life health, proximity of birthplace to a rail line can be used as an instrumental variable (IV) to estimate the impact of migration on late-life mortality. Of course we are concerned about the validity of the exclusion restriction; our biggest concern is that railroads may have brought prosperity to towns, and this in turn improved prospects for lifetime health. We return to this issue in some detail below, arguing that under plausible conditions we can at least credibly bound estimates. This first empirical approach requires data that provide a great deal of detail on place of birth—far more detail than in the primary sources that are generally used for the study of mortality (e.g., Census records, vital statistics, or historical panel survey data). We use administrative data from the Medicare Part B program, which record birth and death dates, matched to files of the Social Security Administration which record “town or county of birth.” We were able to construct records of more than one million individuals for our research—black men and women born in the Deep South, 1916–1932. These data are used in our primary analyses, which focus on mortality rates among the older population (those aged 65 and older), who are included in Medicare data. To evaluate the impact of migration on mortality at younger ages, we turn to a second approach, based on Heckman and Robb’s (1985) “repeated cross-section” evaluation strategy. The idea is quite simple: if moving North has an impact on mortality, then cross-cohort variation in migration rates should be correlated with cross-cohort age-specific mortality. This analysis, which uses data from the 1960 U.S. Census and corresponding death records from Vital Statistics, covers many more birth cohorts (1885–1940) and ages of death (ages 20 to 65) than does our analysis with SSA/Medicare data. The remainder of our paper proceeds as follows: In Section I we present a simple model of selective migration, and discuss strategies for identification of a causal impact of migration on mortality. Section II has a description of data sources. In Section III we present our basic findings about migration patterns of African Americans out of the Deep South, documenting that (i) migratory flows are influenced by rail lines, (ii) most migration is undertaken when individuals are relatively young (prior to age 30), and (iii) migrants tend to have higher education than non-migrants. Section IV then provides our analysis of mortality. We find that survival rates declined among older African Americans as a consequence of migrating North. By examining cause of death, we get some sense about mechanisms involved.