Global financial markets are keenly interested in China's short-term economic direction and policy choices. American policy should look farther. If China chooses to try to stimulate its economy in the second half of the year, even if successful, it will only exacerbate a more pressing long-term challenge.

This challenge in part takes the form of too much money. While attention is focused on when the People's Republic of China (PRC) might catch the U.S. in terms of GDP, it has already passed the U.S. on some measures of its monetary base. Such high liquidity typically precedes periods of stagnation or even outright economic contraction. It is one of the surer reasons for anticipating that China's true economic growth might slow sharply, a possibility that has clear implications for American policy.

Moreover, excess Chinese liquidity has already had an impact in the U.S. The two economies are linked by Beijing's chosen balance-of-payments rules, which tie the yuan to the dollar and compel the PRC to hold excess reserves in American bonds. The U.S. has its own money supply management challenges, and communication between the two countries' monetary authorities will be valuable.