As it has evolved since the days of Adam Smith, modern economic theory drives the actions behind nearly all wealthy countries' central banks. In the United States, the central bank is the Federal Reserve System. The Federal Reserve in the U.S. assumes the role of controlling our nation's monetary policy. Ben Bernanke is the current Chairman of the Fed; he was appointed to succeed Alan Greenspan. The economic policies of our nation are not limited to monetary policy, as macroeconomic policy includes both fiscal and monetary policy. Nations also face tough economic policy decisions with regards to world trade, studies of which are generally undertaken in International Trade and Trade Policy classes. Businesses in all countries have to contend with a web of varying trade policies and variably unfavorable macroeconomic conditions when conducting global commerce. When the transactions costs of such barriers to entry become to high, healthy economic activity decreases.