As Beijing is pressured to halt currency intervention, arguments are generally proposed in terms of the possible benefits to other countries. Such an argument is less compelling than one that points out how China might benefit from an end to its peg against the U.S. dollar. In any event, China's fixed exchange-rate policy is based upon a misperception about the best way for economies to grow.

It turns out that Beijing is following a contradictory set of policies that paradoxically undermine its own economy while propping up the U.S. economy by accommodating the pump-priming of America's central bank.

China, along with other countries, holds huge stocks of dollars in reserves. For their part, China and Hong Kong are the largest net purchasers of Treasury securities and have spent $290 billion on them. If not for these purchases, U.S. Treasury bond yields would be significantly higher and America's ill-fated monetary expansion would have limited ostensible effects.

In an ironic historical twist, China's shift from a command economy has re-created the essential elements of mercantilism. Instead of measuring wealth in terms of gold stocks like the mercantilists, Beijing developed a dollar fetish. Similarly, there is an obsession with export-led growth.

More than two centuries ago, Adam Smith debunked two notions: first, that the wealth of a country reflects its productive capacities; and second, that this wealth can be enhanced by simply trading with other countries. In particular, he portrayed the greatest gains from trade arising from importing rather than exporting.

China's growing foreign exchange reserves are creating domestic inflationary pressures and causing China's public-sector debt to balloon. Since capital controls oblige all exporters to deposit hard currencies in the central bank, they receive either freshly printed yuan (usually in the form of bank deposits) or government debt.

Both arrangements will eventually become untenable by either generating an intolerable rate of inflation or an unacceptable burden of public-sector debt. These represent very high prices to pay to maintain current policies, including the pegged exchange rate.

At present, there is a great deal of volatility in foreign exchange markets. The largest force behind all this turmoil is a weakening U.S. dollar due to a mix of considerations that have induced foreign-exchange brokers to sell Yankee dollars. In the case of the euro, interest arbitrage in the dollar-euro market means that dollars can be borrowed at low interest rates and traded for euros to buy euro-denominated assets with relatively higher yields. While the U.S. Federal Reserve has aggressively slashed interest rates, the European Central Bank has been reluctant to match the cuts.

It turns out that the valuation of a currency is only one element in the competitive nature of an economy. The bad news is that leaders of countries with stronger currencies must develop the political will to carry out structural reforms or their economies will continue to under-perform. Resistance to reforms aimed at reducing the costs of welfare and pension systems as well as halting rising labor costs mean that health and pension payments will keep labor costs high, especially in Europe. In the eurozone area, insufficient competitive pressures and price rigidities push up domestic prices while hindering output and job growth.

A currency can appreciate while the economy remains sluggish, or it can depreciate despite robust growth. As it is, the valuation of a country's currency is not so much determined by the performance of its economy than by the forces of supply and demand on foreign currency markets. For a given supply of money, an increase in the production of goods will increase the exchange value of a currency since each unit will buy more goods. Likewise, increasing the supply of money relative to a fixed output of goods will lead to a decline in the purchasing power of money as each currency unit buys fewer goods.

So it is nonsense to declare before the fact that China's currency is undervalued. We can only know that once all economic players are able to decide where they wish to place their financial assets. Given the relatively high rate of growth in China's money supply, there could be considerable pressures for the yuan to depreciate. This is because a growth rate of the money supply that exceeds the growth rate of economic activity tends to cause the rate of exchange to fall.

Even if exchange rates are fixed but capital can move freely, capital flight from the country tends to put pressure on ending loose monetary policies.

When exchange rates are determined by supply and demand, imbalances can continue for a long time only if most central banks coordinate their policy stances. Once they stop following similar monetary policies, an exchange value of a currency can drop sharply. In the worst case, the collapse of the exchange rate can trigger a severe shock to the real side of the domestic economy.

What is happening with respect to international valuations of the dollar at the moment is that America's central bankers are pumping more money into the system than are most of its trading partners. So, the dollar will continue to weaken until the rate of increase in new money into the U.S. economy no longer exceeds domestic economic growth. And it will have to come into line with the pace of monetary expansion followed by central banks in the rest of the world.