Health Selectivity and Rural-Urban Migration in China: A Nationwide Multiple Cross-Sectional Study in 2012, 2014, 2016

<i>Background</i>: China is undergoing an unprecedented rural-urban migration, which may deeply influence the health of internal migrants. Previous studies suggested that migrants are a selectively healthier population. This paper examines the evidence for and the changes of health selectivity among Chinese internal migrants. <i>Methods</i>: We use data from the China Labor-force Dynamics Survey (CLDS), a nationally representative survey conducted in 2012, 2014, and 2016, respectively. The health statuses of four groups of research subjects (out-migrants, returned migrants, rural residents, and urban residents) are measured by general health, physical health, and emotional health. <i>Results</i>: By comparing the health status of migrants with that of rural residents, we find supportive evidence for the Healthy Migrant Hypothesis that migrants exhibit better health than rural residents in their hometown. We also add strength to the Salmon Bias Hypothesis that migrants returning to their hometowns are less healthy than those still being outside. However, migrants present worse emotional health in both comparisons. The general and physical health gaps between migrants, rural residents, and returnees widened in all three rounds of the survey, which implies a possibly increasing trend of health selectivity. This study also suggests that bringing family to the destination requires better general and physical health, but not emotional health. <i>Conclusions</i>: Migrants are positively selected on general and physical health. The health selectivity in 2012-2016 is highly likely to increase, which means that there are increasing number of obstacles for migrants to overcome. Family migration's high requirement for health might also contribute to it. It is urgent to establish and improve primary health care service systems in rural areas in current circumstances.