The global economic growth that has taken place since the 1970s—with a quadrupling of global economic output—has reshuffled the social deck around the world. The middle classes in the so-called “emerging market” countries are larger, richer, better educated and more technologically connected than ever before.

This has huge implications for China, whose middle-class population now numbers in the hundreds of millions and constitutes perhaps a third of the total. These are the people who communicate by Sina Weibo—the Chinese Twitter—and have grown accustomed to exposing and complaining about the arrogance and duplicity of the government and Party elite. They want a freer society, though it is not clear they necessarily want one-person, one-vote democracy in the near term.

This group will come under particular stress in the coming decade as China struggles to move from middle- to high-income status. Economic growth rates have already started to slow over the past two years and will inevitably revert to a more modest level as the country’s economy matures. The industrial job machine that the regime has created since 1978 will no longer serve the aspirations of this population. It is already the case that China produces some six million to seven million new college graduates each year, whose job prospects are dimmer than those of their working-class parents. If ever there was a threatening gap between rapidly rising expectations and a disappointing reality, it will emerge in China over the next few years, with vast implications for the country’s stability.

There, as in other parts of the developing world, the rise of a new middle class underlies the phenomenon described by Moises Naím of the Carnegie Endowment as the “end of power.” The middle classes have been on the front lines of opposition to abuses of power, whether by authoritarian or democratic regimes. The challenge for them is to turn their protest movements into durable political change, expressed in the form of new institutions and policies. In Latin America, Chile has been a star performer with regard to economic growth and the effectiveness of its democratic political system. Nonetheless, recent years have seen an explosion of protests by high-school students who have pointed to the failings of the country’s public education system.