Fertility decline has fueled a sharp increase in the proportion of 'missing girls' in China, so an increasing share of males will fail to marry, and will face old age without the support normally provided by wives and children. This paper shows that historically, China has had nearly-universal marriage for women and a very competitive market for men. Lower-educated men experience higher rates of bachelorhood while women favor men with better prospects, migrating if needed from poorer to wealthier areas. The authors examine the anticipated effects of this combination of bride shortage and hypergamy, for different regions of China. Their projections indicate that unmarried males will likely be concentrated in poorer provinces with low fiscal ability to provide social protection to their citizens. Such geographic concentration of unmarried males could be socially disruptive, and the paper s findings suggest a need to expand the coverage of social protection programs financed substantially by the central government.