Test of the ‘healthy migrant hypothesis’: A longitudinal analysis of health selectivity of internal migration in Indonesia☆
Introduction
Migration and health have each received a significant amount of attention in social sciences. However, only recently have researchers examined the link between these two population processes. Evidence indicates that migration and health are intertwined in complex ways. Health can impact the decision to move and migration may affect the health of those who move, those who stay, and perhaps even those who host migrants (Hull, 1979). Studying health in the context of migration offers a better understanding of the complexity and diversity of the migration process which is critical, as migration has become a widespread and persistent phenomenon that is changing the structure of family units, communities and societies in our modern world.
Previous work on migration and health largely compares the health of immigrants to that of the native population at destination. Such studies usually find that immigrants are generally healthier than the native-born populations as indicated by mortality rates, chronic conditions, mental health, etc., though the advantage enjoyed by immigrants tends to deteriorate over time (Anson, 2004, Feranil, 2005, Marmot et al., 1984a, Marmot et al., 1984b, Palloni and Morenoff, 2001). This is often referred to as the “epidemiological paradox”, as immigrants usually face disadvantages in many aspects that have negative implications for health.
One of the most frequently offered explanations is the “healthy migrant hypothesis”. It states that migrants represent a selectively healthy group that is not representative of all potential migrants from origin societies (Palloni & Morenoff, 2001). As a result, their health advantage stands out when they are compared with the general population at destination. However, this theory has been purely speculative and inadequately tested. This is in clear contrast to the abundant research on the selection of migration with respect to demographic and socioeconomic characteristics. In fact, in almost none is there an attempt to compare the health of migrants with that of populations in sending communities other than the U.S. This is largely due to the lack of adequate data, which require collecting information on the population from the home region prior to migration.
In addition, although similar theories pertaining to internal migration have been advanced, there is surprisingly limited evidence on how the health status differs between migrants and non-migrants, and almost none on how health considerations may come into play in the decision-making for internal migration. This is unfortunate since the vast majority of migration streams involves movements within national boundaries. Taking Indonesia, the study setting, for example, over 23 million Indonesians migrate each year, but only 10% of these migrants move internationally. This situation calls for the need for more attention on internal migration.
This research represents one of the first attempts to examine the potential influence of health on the likelihood of and reason for migration. An explicit test of the “healthy migrant hypothesis” is crucial for a sound understanding of health disparities between migrants and native population, because it enables us to disentangle the impact of migration on health from the health selectivity effects. By contrast, most earlier work establishing an “epidemiological paradox” inevitably confounds these two aspects due to their exclusive focus on health status after migration.
I first propose an integrated theoretical framework for understanding the implications of health for internal as well as international migration. I then explicitly assess the health selectivity of migration by comparing the pre-migration health status between those from the sending population who do and do not move. I focus on the important but inadequately researched phenomena, internal migration, for which data on comparable non-migrant population are more readily available. Data used are from the Indonesia Family Life Survey (IFLS), a national representative longitudinal sample survey conducted in 1993, 1997, and 2000. The longitudinal structure and the detailed migration histories facilitate the examination of my research questions. I further distinguish different types of migration to take account of substantial heterogeneity among migrants, and various dimensions of health given that they may have different implications for migratory decisions. Adjustment for household unobserved heterogeneity, which may contaminate the relationship, is built into the analysis via household fixed-effects.
Indonesia, the fourth most populous nation in the world, is drawn on as a case study. The country has enjoyed rapid economic growth over the past three decades, along with concomitant improvements in access to health care and common measures of health status such as life expectancy and infant mortality rate (Frankenberg and Thomas, 2000, Muhidin, 2002). With respect to migration, Indonesia is recognized as one of the world's major sources of unskilled migrant workers to Southeast Asian countries (Hugo, 2005, Sukamdi and Brownlee, 1998). As the industrialization process has intensified, geographical mobility within the country also has increased in recent years (Hugo, 2005, Muhidin, 2002).1 In the most recent census, 1 in 10 Indonesians was classified as a migrant. This stream is largely characterized by rural to urban and economically motivated migration, with the largest cities as the main destinations. A few studies have examined the characteristics of internal migrants in Indonesia (Muhidin, 2002, Speare and Harris, 1986), which suggest that migrant workers are drawn disproportionately from young adult males who are better educated and from relatively poor households.
Section snippets
Analytic framework
Since migration often involves disruption of individual's life and adaptation to a new environment, migrants tend to be selective for personal characteristics that foster their ability to handle change and adapt to new environments. This has been demonstrated in both the internal and international migration literature (De Jong et al., 1983, Massey, 1988). Aside from a variety of demographic and socioeconomic characteristics, physical health is likely to be one of the selection factors (Evans,
Data
Data used are from the 1997 and 2000 waves of the Indonesia Family Life Survey (IFLS), a high-quality panel survey of individuals, households and communities. To maximize representation of the population, the IFLS was conducted in 13 out of 27 provinces in Indonesia, representing 83% of the population. The first round (IFLS1) was collected in 1993 using multi-stage probability sampling and it included interviews with 7224 households and with 22,347 individuals (Frankenberg & Karoly, 1995). In
Descriptive statistics
Table 1 presents descriptive statistics for the analytic sample with complete information on all variables, separately for two age groups. There are substantial differences by age. The overall rate of migration is significantly higher for the younger group (11%) than for the older group (3%). Note that the number of migrants in the older group is small, which may limit the statistical power of this analysis.
There are also noticeable differences by purpose of migration, with younger people more
Discussion
This paper examines whether health conditions are associated with migration decisions in the context of a growing migration population in Indonesia. It represents one of the first attempts to formally test the “healthy migrant hypothesis” by incorporating pre-migration health information on people who move and who stay.
I find support for the conjecture that, in addition to demographic and socioeconomic factors, health considerations also play a role in migration decision-making. But the
Acknowledgements
The author would like to thank Donald J. Treiman, William M. Mason, Elizabeth Frankenberg, and Naihua Duan for their contributions at earlier stages of this work.
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An early version of this paper was presented at the Annual Meeting of the Population Association of America, New York, March 29–31, 2007.