AMONG those with most to celebrate as the Chinese Communist Party marks its 90th birthday on July 1st are the country’s bourgeois reactionaries. Perhaps now the most important pillar of the party’s support, China’s middle class was virtually non-existent until it was recreated in the late 1990s. So far, the communists have amply fulfilled their side of a tacit bargain in which well-off city-dwellers have traded political choice for fast-growing prosperity. But as the economy slows over the next decade, the party will struggle to keep its word. Indeed, peace and prosperity may depend on the very sort of political reform the party has tried so hard to avoid.