Today's column is about the factors that seem to point to a slowdown in extraordinary Chinese growth. The leadership wants the economy to continue expanding at an annual pace of 10 percent or so, but it will be increasingly challenging for the economy to accomplish that. Part of it is just the tyranny of arithmetic. As growth keeps compounding and per-capita incomes draw closer to the global mean, it's harder to keep up the pace. (Of course, however, much of China is still poor by world standards. Its per-capita GDP of $6,800 is a small fraction of the United States' $46,000, according to IMF figures.)

I didn't have room in the column to get into a Chinese slowdown's implications, which would be powerful and mixed. The immediate effect -- a slowing of the growth in living standards, of the rate at which people are rising from poverty -- would be negative. And if it destabilized the regime, or even if it made the leadership feel threatened, a Chinese "growth recession" (nobody is predicting the economy to actually shrink anytime soon; a big setback for China would be for growth to fall below 7 percent) could have dire global effects. You could expect to see tensions rise over Taiwan and other Beijing territorial claims, as the regime sought to distract attention from a disappointing economy. Any economic setback is unlikely to stop China from continuing to build up its military.

Some in Washington are worried about China's rise as a global competitor, but an economically struggling China might pose an even bigger threat. North Korea has one of the weakest, most miserable economies in the world, but that hasn't stopped -- indeed it has everything to do with -- it being a very dangerous global actor. The best outcome for China and Washington would be for China to let the renminbi rise to its natural value. That would level the playing field for international trade. But it would also raise China's standard of living versus the world, let the Chinese buy more from United States and other nations and set the stage for the rise of a consumer economy and the next stage of China's growth.