假设美国净外债占美国GDP总量的25%，这些债务每年会产生5%的利息。每年支付于净外债的利息会对美

国的GDP (以百分比计)形成巨额的负担吗？你认为这是一个庞大的数字吗？如果净外债为GDP的100%呢？你认为一国的外债规模发展到何种程度，就应该引起政府的担忧？

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？