Amid the demographic news about the world's population reaching seven billion—either now or in a few months, depending on whose count you trust—the Chinese news agency Xinhua carried a story about population trends in China, and two significant trends in particular. One is the aging of the Chinese population, with fertility too low to offset increases in the ranks of the elderly. The other is a large gender imbalance—rooted chiefly in one-child policies and gender-selective abortion—that is becoming more prominent in the adult population. There are about 15 million more males than females today in China. The imbalance will become more pronounced over the next ten years, with an estimated 30 million men during that period being unable to find brides and get married.

Chinese leaders have some major challenges ahead, rooted in this demography. The growing burden of a large elderly population requiring support from its younger, still-working brethren can become a drag on economic growth. The experience of graying Japan over the past couple of decades is one that Chinese leaders surely want to avoid. As for the gender ratio, a surplus of unmarried young adult males has historically been associated with instability and a propensity for violence both internally and externally. Unmarried males are, for example, disproportionately numerous in the ranks of terrorists. Past Israeli efforts to put Palestinian terrorists on a more peaceful path have emphasized getting them married.

While the potential difficulties for Beijing are clear, the implications for the West are not. These demographic patterns in China could cut different ways for Western security interests. Insofar as Beijing is more preoccupied with internal problems and its growth slows, the larger rise of China and the threat it may pose is lessened. And if some of those unmarried men become societal misfits, the authority against which they rebel would be China's own. The implications of those dimensions are largely positive for the West.

An offsetting negative dimension is that the gender imbalance, and the tendency of such an imbalance to be associated with instability and authoritarianism, will work against any hoped-for evolution of Chinese politics and society in a Western direction. Even worse would be military adventurism to occupy and work off the steam and frustrations of the unmarried males—another effect seen of gender imbalance in the past.

All hard to predict, but worth watching.