Financial economics plays a far more prominent role in the training of economists than it did even a few years ago. This change is generally attributed to the parallel transformation in capital markets that has occurred in recent years. It is true that trillions of dollars of assets are traded daily in ¯nancial markets|for derivative securities like options and futures, for example|that hardly existed a decade ago. However, it is less obvious how important these changes are. Insofar as derivative securities can be valued by arbitrage, such securities only duplicate primary securities
