经济学前沿复习资料

Golden Rule savings rate

In economics, the Golden Rule savings rate is the rate of savings which maximizes steady state level or growth of consumption,[1] as for example in the Solow growth model. Although the concept can be found earlier in John von Neumann and Maurice Allais's works, the term is generally attributed to Edmund Phelps who wrote in 1961 that the Golden Rule "do unto others as you would have them do unto you" could be applied inter-generationally inside the model to arrive at some form of "optimum", or put simply "do unto future generations as we hope previous generations did unto us."[2]

In the Solow growth model, a steady state savings rate of 100% implies that all income is going to investment capital for future production, implying a steady state consumption level of zero. A savings rate of 0% implies that no new investment capital is being created, so that the capital stock depreciates without replacement. This makes a steady state unsustainable except at zero output, which again implies a consumption level of zero. Somewhere in between is the "Golden Rule" level of savings, where the savings propensity is such that per-capita consumption is at its maximum possible constant value. Put another way, the golden-rule capital stock relates to the highest level of permanent consumption which can be sustained. Inter-temporal tradeoffs

NAIRU and rational expectations

In the 1970s, new theories, such as rational expectations and the NAIRU (non-accelerating inflation rate of unemployment) arose to explain how stagflation could occur. The latter theory, also known as the "natural rate of unemployment", distinguished between the "short-term" Phillips curve and the "long-term" one. The short-term Phillips Curve looked like a normal Phillips Curve, but shifted in the long run as expectations changed. In the long run, only a single rate of unemployment (the NAIRU or "natural" rate) was consistent with a stable inflation rate. The long-run Phillips Curve was thus vertical, so there was no trade-off between inflation and unemployment.

The expectations-augmented Phillips curve introduces adaptive expectations into the Phillips curve. These adaptive expectations, which date form Irving Fisher’s book “The Purchasing Power of Money”, 1911, where introduced into the Phillips curve by monetarists, specially Milton Friedman. Therefore, we could say that the expectations-augmented Phillips curve was first used to explain the monetarists’ view of the Phillips curve.

Adaptive expectations models led to an important shift in the perception of a government’s ability to act. Under Keynes’money illusion, changes in nominal variables (prices, wages, etc…) were accepted by age nts as real despite overall purchasing power remaining stable.

However, monetarism embraced the adaptive expectations theory to mean that people