Writing in the New York Times, Simon Johnson, an economist at MIT, makes the argument that people outside the United States may at some point decide to "save less (in which case they may hold onto their existing United States government debt but not want to buy so much of new issues)." What does saving by people outside of the United States have to do with sales of U.S. government debt? Does the level of domestic investment occurring in foreign countries matter for your answer? Briefly explain.