The rise in China’s sex ratio at birth during the last two decades has had a wide range of economic and social consequences including excessive savings as families with boys compete to match their sons with scarce girls and rising disaffection and crime amongst the unmarried male population. These consequences are analysed using a global dynamic model that projects demographic behaviour and economic performance through to 2030. The results show that the proportion of unmatched unskilled Chinese men of reproductive age could be as high as one in four by that time, unless effective policies are put in place to rebalance the sex ratio at birth. Even then, it will take decades to reduce the sex ratio in the general population. This will come at a cost in terms of economic growth via the impact on reduced savings, although a lower saving rate offers some rebalancing on a global scale. Moreover, the results suggest that more than offsetting gains could accrue from productivity improvements stemming from reduced crime.