It would be convenient if global demographics were distributed in such a way that aging countries could run surpluses just when younger countries needed the capital. In reality, many major economies will be trying to save for retirement at the same time.
要是全球人口结构的扩散结构是年轻国家需要资本，同时恰好老龄化国家保持盈余，那么问题就迎刃而解了。在现实中，许多主要经济体会同时为退休而储蓄。此外，年轻国家通常是新兴市场国家，既无规模，也无能力有效吸收世界过剩储蓄。