The default framework for thinking about these questions is a very old one: the market-and-natural-interest-rate framework of Knut Wicksell’s Geldzins und Guterpreis (“Interest and Prices”). In every economy, the argument goes, there is a market interest rate determined by the financial system, and there is a natural interest rate – the value at which desired savings at full employment equal desired investment at full employment, and at which the economy as a whole desires neither to leverage nor to deleverage.
思考这些问题的默认框架是非常古老的思想：维克塞尔（Knut Wicksell）的《利息与价格》（Geldzins und Guterpreis）中的市场和自然利率框架。该观点指出，在每一个经济都有一个由金融系统决定市场利率和一个自然利率，自然利率即充分就业时的期望储蓄等于充分就业时的期望投资的利率值，亦即经济作为一个整体既不需要杠杆也不需要去杠杆的利率值。