In the past decade, some observers have noted an unusual aspect of the Mexican peso's behavior: During periods when the U.S. dollar has risen (fallen) against other major currencies such as the euro, the peso has risen (fallen) against the dollar. Very few other currencies display this behavior....

Among the various explanations for the runup in oil and commodity prices of recent years, one story focuses on the role of monetary policy in the United States and in developing economies. In this view, developing countries that peg their currencies to the dollar were forced to ease their...