The foreign savings glut: inordinate savers or thriving traders?

In the years prior to our recent economic crisis, foreign savings poured into the United States. Did foreign traders who happened to acquire dollars from American trade deficits merely choose to keep these funds in dollar-denominated assets? Or, did foreigners decide to increase their savings inordinately and place those funds in dollar-denominated assets? The answer is key to the debate about the sources of liquidity that paved the way to our recent economic problems.