Eventually, declines in fertility rates and increases in longevity may lead to similar issues with aging populations in what is currently the developing world but likely only well after the demographic transition in the United States and other developed nations. *  *  *  The aging of the population in the United States will significantly affect our fiscal situation.
That is: independent monetary policies are possible if, and only if, the capital account is managed, directly or indirectly, via macroprudential policies. These could include capital controls if macroprudential policies are insufficient. In other words: flexible exchange rates do not ensure independent monetary policies when capital is highly mobile.