Why the Global Shortage of Safe Assets Matters by David Beckworth

In the early-to-mid 2000s, the Fed exacerbated the asset-shortage problem as its loose monetary policy got exported via fixed exchange rates to much of the emerging market world which in turn recycled it back to the U.S. economy via the "global saving glut" demand for safe assets. (For more on this point see this post and my paper with Chris Crowe.) Since late 2008, both the Fed and the ECB have worsened the asset-shortage problem by failing to first prevent and then restore nominal income in each region to its expected path. In other words, since 2008 both the Fed and the ECB have passively tightened monetary policy and this has caused some of the AAA-rated securities to disappear. (Yes, some of the AAA-rated MBS and sovereign debt would have defaulted on their own, but some of them like French sovereigns would have maintained their safe asset status were it not for insufficient aggregate demand caused by passively tight monetary policy.)

I would look into the "loose monetary policy" and the context of it.