Interesting observation by Pierre-Olivier Gourinchas, a research associate at the NBER:
In recent theoretical work, Caballero, Farhi, and I show that the safe-asset scarcity mutates at the ZLB [Zero Lower Bound], from a benign phenomenon that depresses risk-free rates to a malign one where interest rates cannot equilibrate asset markets any longer, leading to a global recession. The reason is that the decline in output reduces net-asset demand more than asset supply. Hence our analysis predicts the emergence of potentially persistent global-liquidity traps, a situation that actually exists in most of the advanced economies today.
…..our results point to a modern — and more sinister — version of the Triffin dilemma. As the world economy grows faster than that of the U.S., so does the global demand for safe assets relative to their supply. This depresses global interest rates and could push the global economy into a persistent ZLB environment, a form of secular stagnation.
Source: The Structure of the International Monetary System | NBER