How did we get here? Ben Bernanke

At the most basic level, the role of banks and other financial institutions is to take the savings generated by households and businesses and put them to use by making loans and investments. In our global financial system, saving need not be generated in the country in which it is put to work. In the past 10 to 15 years, the United States and some other industrial countries have been the recipients of a great deal of foreign saving. Indeed, the net inflow of foreign saving to the United States reached about 6% of national output in 2006, an amount equal to about $825 billion in today's dollars.....