The American blogosphere lit up this week with discussion of a report from the International Monetary Fund that, by some measures, the Chinese economy will be bigger than the U.S. economy by 2016. It makes a great headline, but that story was, of course, old news: Given China’s size, and the speed with which it is growing, simple arithmetic tells you that its economy will one day be bigger than that of the United States. The only question is when.