In 1898, Swedish economist Knut Wicksell argued that there existed a “natural” rate of interest that balanced the supply and demand of credit, assuring the appropriate allocation of saving and investment. Should market interest rates remain below the natural rate for an extended period, investors will borrow excessively, allocating capital into less productive investments and ultimately into purely speculative ones.

This is what the economy faces today after years of meagre borrowing costs. Policymakers have created a Wicksellian dilemma where investment spurred by low interest rates is driving economic growth, but these inefficient investments support growth at the expense of lower productivity in the economy. In recent years, this investment has flowed into housing, commercial real estate and equities, driving asset prices higher, exactly the goal of the Central Banks in the wake of the financial crisis. But as the recovery in real estate and equities matures, a darker side of this imbalance between natural and market rates is beginning to emerge. Many investments today using artificially cheap capital are not increasing productivity — they are being made because money is cheap and the profit motive is strong.

The harsh reality is extended periods of malinvestment result in declining productivity growth, lower potential output and slower increases in living standards. A failure to normalise market interest rates soon will result in more capital ploughed into investments that are less productive and more speculative. As productivity declines, long-term growth will be stunted. Eventually, inflationary pressures will build, forcing market interest rates to rise. The longer market rates remain below the natural rate the greater the purge will be once higher rates induce a recession, causing a sharp rise in defaults among malinvestments made during the period of cheap credit.