For good or ill, the world economy is interdependent and becoming more so. The financial system is increasingly able to direct savings in one part of the world toward its most profitable uses in some other part of the world. Yet, the financial crisis of 2008, which started in the U.S. domestic mortgage market, quickly spread to countries: interdependence introduces new risks. Robust foreign trade in goods and services is associated with economic strength and fuels the rapid development of many poor countries. Yet, dependence on trade allows a recession in one country to reduce demand and increase unemployment in other countries. Although these interconnections were introduced in the discussion of national accounts in Chapter 2 and of the financial system in Chapter 6, they present complications that we shall examine more closely in this chapter. In many ways, the world economy is just a bigger version of the national economy. Yet it is complicated by the fact that there are many barriers to international trade, especially in real factors of production, such as labor, and by the existence of different national currencies, which adds considerable complexity to financial markets.