The alarming rise in China’s reported HIV cases in the last decade has caused concern among
government officials and public health researchers. The increase in reported HIV cases is
especially worrying because the majority of new cases are not observed in traditional at-risk
populations (such as intravenous drug users and recipients of former plasma donors), but are
sexually transmitted. This chapter analyzes the demographic patterns in China that may be an
important determinant of the increase in sexually transmitted HIV infections. High sex ratios,
numbers of men relative to numbers of women, in young cohorts of Chinese men and women
contribute to the increasing failure of Chinese men to marry. These men, referred to as “bare
branches (guang gun) since they will be unable to extend the family tree, are more likely to
migrate to regions with more favorable marriage markets, and may be more likely to purchase
sex. This behavior in turn increases men’s risk of sexually transmitted infections, including HIV.
We also analyze how further increases in sex ratios among Chinese men and women of marrying
ages may affect migration patterns, commercial sex demand, and the spread of HIV.
We begin the analysis in section two with a brief history of HIV in China during the last two
decades. In section three, we present forecasts for demographic changes in China in the 21st
century, describing how the entry of cohorts with highly skewed sex ratios into the marriage pool
may result in large numbers of males marrying late, or failing to marry. Section four considers
how the imbalanced sex ratios and socio-economic trends may promote an outmigration from
rural to urban areas in search of wives and jobs. Such groups of young, poor, single men may
have increased sexual risk compared to their rural counterparts. In section ve we present
evidence that areas within China with large numbers of unmarried men are associated with
higher reported rates of purchasing sex among men, and explore via simulation how the failure
of men to marry may increase STI and/or HIV incidence in the future. Section six discusses the
actions currently being taken by the Chinese government to reduce sex ratios at birth and to curb
the spread of HIV in at-risk populations. We conclude in section seven with a brief discussion of
China’s policy options in light of the results of our analysis.