Suppose that the U.S. net foreign debt is 25 percent of U.S. GDP and that foreign assets and liabilities alike pay an interest rate of 5 percent per year. What would be the drain on U.S. GDP (as a percentage) from paying interest on the net foreign debt? Do you think this is a large number? What if the net foreign debt were 100 percent of GDP? At what point do you think a country's government should become worried about the size of its foreign debt?