On the other hand, negative interest rates as a purposeful strategy for managing the economy are something new in the post-WWII world. In theory they can be increased to any amount. That and the unlimited capacity to create money for central banks to use to buy central governments’ debt provide the possibility of staving off economic collapse for an extended period of time yet. The most likely scenario, I think, is economic stagnation along with continued, even increasing growth in total debt until some exogenous shock, probably associated with war (especially cyber warfare) or global warming, causes the financial house of cards that has become the basis of the economy to collapse.