Sex Differences in Mortality Rates Have Increased in China Following the Single-Child Law

  • Daniel J Kruger University of Michigan
  • Stephen P Polanski University of Michigan
Keywords: sex differences, mortality, Operational Sex Ratio, China, single-child law


Male behavior and physiology is designed for enhanced competitiveness at the expense of longevity, resulting in higher mortality rates compared to females in most species. These differences vary across populations consistent with factors indicating the intensity of male mating competition. Reproductive dynamics are strongly influenced by the relative proportions of potentially reproductive males and females in a population. Because the reproductive strategies of men and women are somewhat divergent, market influences on the intensity of mating competition and selectivity for partners produce different outcomes in female biased and male biased populations. The single-child law implemented in China in 1979 has led to increasing proportions of men in the Chinese population. Using historical mortality data, we found a trend for increasing sex differences in Chinese mortality rates from 1982 to 2000. This increase was most prevalent in young adulthood, when male mating competition is most intense as males reach sexual maturity and seek female partners. In contrast, males exhibited more survival gains than females in infancy and early childhood.

Author Biographies

Daniel J Kruger, University of Michigan
Daniel J. Kruger is a Research Assistant Professor at the School of Public Health and Institute for Social Research at the University of Michigan. His evolutionary research interests include: altruism, cooperation, competition, demography, life history, literary Darwinism, mortality patterns, risk taking, and interventions for social and ecological sustainability.
Stephen P Polanski, University of Michigan
Stephen P. Polanski is an undergraduate in the College of Literature, Science, and the Arts at the University of Michigan and a participant in the Undergraduate Research Opportunities Program.
Original Articles